Today we have the Portuguese ‘Pikachu around the World’ part. I will add the same quote again, which I’ll do for all parts:
The first nine parts were Traditional Chinese (click here to go to that part); Dutch (click here to go to that part); English (click here to go to that part); French (click here to go to that part); German (click here to go to that part); Italian (click here to go to that part); Japanese (click here to go to that part); Korean (click here to go to that part); and Polish (click here to go to that part).
The Portuguese portion of my Pikachu collection is 100% complete, mainly because of an amazing Brazilian middleman I met in 2017, who helped me go from 30% on both my Pikachu and Seviper collections, to 100% Seviper and 99% Pikachu, and has helped me with every new Portuguese release since. 
Portuguese
Let me start with a picture of all Portuguese Pikachu cards in my collection:
Unfortunately, I haven’t been able to find any source for Portuguese release dates. If anyone knows any source at all with Portuguese release months + years, I would greatly appreciated it! Huge thanks to everyone who contributed in this thread to figure out the Portuguese release dates, especially @Vertemes (who with just one Bulbapedia-link allowed me to fill in the release dates of roughly half the sets, kickstarting that entire thread) and @AuraBea (who went above and beyond through the Copag archives in hour-long searches, to not only find the missing dates, but also verify most of the ones from Bulbapedia).
Portuguese cards are released in both Portugal and Brazil. During the WotC era, the Portuguese cards were printed by Cartamundi, the WotC facility in Belgium, like all other European language cards. These were in the Brazilian Portuguese language, and distributed to both Portugal and Brazil.
After the WotC era, until 2011, the Portuguese cards were printed in Brazil by Devir Livraria, and distributed within Brazil and to Portugal. These cards were also all in the Brazilian Portuguese language.
Then from 2011 onward, the Portuguese cards were still printed in Brazil, but by the company Copag. Copag also distributed the cards within Brazil, but Devir Livraria still distributed the cards printed by Copag to Portugal, which still holds true to this day with the current Sword & Shields era sets. These cards were also all in the Brazilian Portuguese language.
Also, from what I’ve heard, almost all collectors from Portugal prefer English cards over Portuguese cards though, hence the lack of many useful online sources.. 
The Portuguese sets are a bit of an odd one, kinda like Korean. Its sets and promos are sprinkled in all the eras and appear pretty random, until we’ve reached the XY era of sets.
The first Portuguese set, released somewhere early/mid 2000 (WotC’s release plan in February 1999 was to release the Portuguese Base Set in Brazil in March 2000), is of course the Base Set, with both a 1st and unlimited edition Pikachu.
After that came the Portuguese Jungle set, released around mid 2000 (WotC’s release plan in February 1999 was to release the Portuguese Jungle set in Brazil in May 2000), with a 1st and unlimited edition Pikachu again. (The 1st edition print run of this set is pretty rare and hard to find.)
The only Portugese WotC era Pikachu promo is the #1 Ivy Pikachu promo with golden Pikachu tail stamp, from the Pikachu World Collection 2000, which we’ve mentioned a bunch of times in the other parts. The nine cards in this collection were released at the Summer Olympics in Sydney, Australia between September 12th and October 1st, 2000.
And the final WotC era Portuguese set was the Fossil set, released around late 2000 (WotC’s release plan in February 1999 was to release the Portuguese Fossil set in Brazil in September 2000), lacking any Pikachu cards.
After that the first Portuguese set of the EX era, EX Ruby & Sapphire, was released somewhere in 2004. This set lacked any Pikachu cards.
Next we surprisingly enough have the Portuguese EX Team Rocket Returns set, which was released in Japanese, English, and Portuguese, but none of the other languages. This Portuguese set was probably released somewhere near the start of 2005, and also didn’t contained any Pikachu cards.
Next we have the Portuguese EX Deoxys set, released in August 2005 (source). This set also lacked any Pikachu cards. (This set was pretty short-printed in Portuguese. In fact, I’ve only very recently learned this set was released in Portuguese in the first place.)
Next we have the first four out of twelve Portuguese Half Decks, released in September 2005 in Brazil and October 2005 in Portugal: Mudkip Illustrated Booklet; Torchic Illustrated Booklet; Treecko Illustrated Booklet; and Ralts Illustrated Booklet. The first four Half Decks were also released in Spanish, and the other eight were exclusively released in Portuguese. None of these decks contained any new cards however. These first four Half Decks contained cards from the earlier mentioned Portuguese EX Ruby & Sapphire set.
After that we have the Portuguese EX Emerald set, released in early December 2005 (source1; source2), containing a Pikachu Reverse Holofoil and all three non-Holo EX era codes.
After that we had the Portuguese POP Series 2 mini set, which I assume is released in late 2005. This mini set did contain a Pikachu card.
The next two Portuguese-exclusive Theme decks were the Exploud Illustrated Booklet and Rayquaza Illustrated Booklet, released separately in March and April 2006 respectively, which contained cards from the earlier mentioned EX Emerald set.
After that came the Portuguese EX Unseen Forces set, likely release in early/mid 2006, which lacked any Pikachu cards.
Likely released in early/mid 2006 as well was the Portuguese POP Series 3, also lacking any Pikachu cards.
Next two more Portuguese-exclusive Theme decks: Ho-Oh Illustrated Booklet and Lugia Illustrated Booklet, released separately in May and June 2006 respectively, both containing cards from the earlier mentioned Portuguese EX Unseen Forces set.
After that we had the Portuguese EX Legend Maker set, likely released somewhere in mid 2006. The Secret Rare box topper Pikachu of this set wasn’t released in Portuguese, so for that reason this Portuguese set also lacked any Pikachu cards.
The POP Series 4 was also released in Portuguese, like somewhere in mid/late 2006. This mini set did include a non-holo Pikachu card.
Next we have the Diamond & Pearl era, of which the first set by the same name was likely released in Portuguese somewhere in mid 2007. From the DP era onward up to and including the XY era, all Portuguese sets lacked Reverse Holos. This set was also without any Pikachu cards.
The next DP era set Mysterious Treasures was released in Portuguese as well, likely released somewhere in early 2008. This set did contain a Pikachu card.
Then we have the final four Portuguese-exclusive theme decks: Machamp Illustrated Booklet; Gengar Illustrated Booklet; Golem Illustrated Booklet; and Omastar Illustrated Booklet. The Machamp and Gengar decks were released somewhere in mid/late October 2008 (source: first mentioned on the Devir news page, somewhere between October 3rd and 21st, 2008). And the Golem and Omastar decks in December 2008.
Next it’s quiet again with Portuguese set releases, but we did have the two Portuguese Pikachu cards from the Pikachu World Collection 2010, of which the Japanese version was released on July 8th, 2010 and the English one in November 2010, as mentioned a few times before in earlier parts. Fun fact: these are the only Portuguese cards printed in the Portuguese language from Portugal, rather than Brazilian Portuguese like all other Portuguese Pokémon TCG cards.
Then we had the Portuguese Secret Wonders set, released in late January 2011 (source1; source2; source3). This set lacked both Pikachu cards and Reverse Holos.
The next Portuguese set release was in the Heart & Gold era, with the set by the same name being released on July 15th, 2011 (source1; source2). This set also included a Pikachu card, but again only in non-Holo since this entire era didn’t had any Portuguese Reverse Holos either.
The second HSS era set Unleashed was released in Portuguese as well, on September 26th, 2011 (source1; source2). This set didn’t contained any Pikachu cards.
Next we skip to the Black & White era, for which the McDonald’s Collection 2011 were the first to release in Portuguese in Brazil on November 3rd, 2011 (source). This mini set lacked any Pikachu cards
Next we have the Black & White set itself, released on December 1st, 2011 (source). This set included a Secret Rare Pikachu card.
Next is the Portuguese Emerging Powers set, released on April 5th, 2012 (source1; source2), which didn’t contain any Pikachu cards.
Then came the Portuguese Noble Victories set, released on June 27th, 2012 (source1; source2), which also lacked any Pikachu cards.
Followed by the McDonald’s Collection 2012, which started on September 27th, 2012 (source). This mini McDonald’s set lacked Pikachu cards as well.
The next Portuguese BW era set was Next Destinies, released on October 5th, 2012 (source1; source2), which did contain a non-Holo Pikachu again. The Portuguese sets for the BW era still didn’t contained any Reverse Holos.
Then we had the Portuguese Dark Explorers set, released on January 18th, 2013 (source), which also lacked any Pikachu cards.
The same applies to the Portuguese Dragons Exalted set of April 22nd, 2013 (source).
The next Portuguese BW era set was Boundaries Crossed, released on April 22nd, 2013 (source), which did contain a Pikachu card.
Next we have the Portuguese Plasma sets to close off the BW era, all three lacking any Pikachu cards:
- Plasma Storm, released on September 30th, 2013 (source);
- Plasma Freeze, released on December 27th, 2013 (source);
- Plasma Blast, released on March 12th, 2013 (source).
Next we have the XY era, at which point the Portuguese releases became more active and consistent (although this entire era still didn’t contained any Portuguese Reverse Holos either). The Portuguese sets were usually released 2-6 weeks after its English release.
We start with the Portuguese XY set of May 23rd, 2014 (source), which contained a Pikachu card.
Next we have the Portuguese Flashfire set, released on September 12th, 2014 (source). This set didn’t contained any Pikachu cards.
Released on December 5th, 2014 (source) is the Portuguese Furious Fists set, which did contain a Pikachu.
Then on February 20th, 2015 (source) we had the Portuguese Phantom Forces set. This set lacked any Pikachu cards, though.
Next on May 15th, 2015 (source) was the Portuguese Primal Clash set, also without any Pikachu cards.
The same applied to the smaller Portuguese Double Crisis mini set of July 24th, 2015 (source).
The Portuguese Roaring Skies set set of August 14th, 2015 (source) did contain a Pikachu card however.
And the final Portuguese set of 2015 is Ancient Origins, released on October 30th, 2015 (source), but again without any Pikachu cards.
Next we have the Portuguese BREAKthrough set of January 22nd, 2016 (source), which did contain a Pikachu card.
Next, on the 20th Pokémon Day - February 27th, 2016 (source1; source2), was the Holofoil XY95 Pikachu promo. Thanks to Bulbapedia, I can at least give some release information about this Brazilian-exclusive Portuguese card. The earlier mentioned distributer Copag organized events at select stores in Brazil. Each store received 55 copies of this XY95 Pikachu promo; 3 Badge cases; 3 bags with Play! Pokémon logo; and 12 Mewtwo deck boxes. Exclusive merchandise was also available at these tournaments. This Pikachu promo was also given to customers at RiHappy, PB Kids, BMart, and Planeta Bringuedos stores on February 27th and 28th, 2016, when they bought at least two Pokémon TCG products - excluding loose booster packs (which were only ~1 USD each in Brazil and contained just five cards).
Next on April 8th, 2018 (source) we have the Portuguese BREAKpoint set, lacking any Pikachu cards.
Next on April 29th, 2016 (source) is the Portuguese XY84 Pikachu EX promo, which just like the other languages came in Pikachu EX Legendary Collection boxes.
The Portuguese Generations set did contain both a non-Holo and Full Art Pikachu card, released on May 13rd, 2016 (source1; source2).
Next we have the Portuguese Fates Collide set of July 22nd, 2016 (source), lacking any Pikachu cards.
The XY Trainer Kit: Pikachu Libre & Suicune was released in Portuguese as well somewhere in September 2016 (source), which of course contains both a non-Holo and Holofoil Pikachu Libre card.
And the final Portuguese XY era set that was released was Steam Siege, released on October 28th, 2016 (source), also without any Pikachu cards.
Another XY era Pikachu promo was the XY124 Full Art Pikachu EX, released inside the Pikachu EX Red & Blue Collection box in November 2016 (source1; source2). This card wasn’t released as a Jumbo, unlike the same card that came from European releases.
And the final Portuguese XY Pikachu EX promo was the XY174 Pikachu EX, which came in the Pikachu Battle Heart Tins, likely released somewhere in September/October/November 2016.
Next we have the Sun & Moon era, at which point Portuguese Reverse Holos finally returned.
The first Portuguese Sun & Moon era set is the set by the same name, released on February 10th, 2017 (source1; source2), came without any Pikachu cards.
Next we have the Portuguese Guardians Rising set of May 12th, 2017 (source1; source2), also lacking any Pikachu cards.
The XY Evolutions set wasn’t released in Portuguese, but there was a very short Easter promotion for the Portuguese XY Evolutions Venusaur EX; Charizard EX; Blastoise EX; Pidgeot EX; Slowbro EX: Dragonite EX; and Mewtwo EX. Those are the only seven Portuguese XY Evolution cards that were released, inside a plastic Easter egg product, available between March 29th and April 16th, 2017 (source) by spending at least 60 R$ (~19 USD) on other products, and then spending an additional 10 R$ (~3.25 USD) for this Easter egg at RiHappy stores in Brazil. Each Easter egg contained one of the mentioned Portuguese XY Evolutions cards and six Double Crisis cards at random.
Then on June 23rd, 2017 (source) we also had the SM Trainer Kit: Lycanroc & Alolan Raichu, of which the Alolan Raichu Half Deck contained two differently numbered Pikachu cards with the same artwork.
Followed by the Portuguese Burning Shadows set of August 4th, 2017 (source1; source2), which did have a Pikachu in it, both as non-Holo and Reverse Holo.
Next on October 13th, 2017 (source) we had the Portuguese Shining Legends set, which again contained Pikachu cards.
The Let’s Play, Pikachu! Theme Deck that’s likely released in October or November 2017, containing a Shattered Holofoil version of this Pikachu artwork, was released in Portuguese as well.
This artwork was also used inside the McDonald’s Collection 2019 mini set, likely released near the end of 2019.
On that same day, October 13th, 2017 (source) accompanying the Shining Legends set, we also had the four Portuguese Shining Legends three-pack blisters, one of which containing the Holofoil SM76 Pikachu promo.
Then the next Portuguese set was Crimson Invasion, released on November 3rd, 2017 (source1; source2), which contained a non-holo and Reverse Holo Pikachu.
Two days later, on November 5th, 2017 (source) we also had the non-Holo SM108 Ash’s Pikachu promo, given as part of the 20th Pokémon movie: I Choose You! cinematic release.
Then we had the Portuguese Shining Legends Super-Premium Collection box, containing the Holofoil SM81 Pikachu promo, which was released on November 30th, 2017 (source).
Followed by the Portuguese Ultra Prism set of February 2nd, 2018 (source), without any Pikachu cards.
The same applies to the next few Portuguese set again:
- Forbidden Light, released on May 4th, 2018 (source);
- Celestial Storm, released on August 3rd, 2018 (source1; source2);
- Dragon Majesty, released on September 7th, 2018 (source);
- Lost Thunder, released on November 2nd, 2018 (source1; source2).
Released somewhere in November/December 2018, we had the Holofoil SM157 Pikachu promo (with a nice swirl on my copy 
), released inside the Portuguese Pikachu & Eevee Pokéball Collection box.
The first Portuguese set from 2019, on February 1st, 2019 (source1; source2; source3) to be exact, is the Teams Up set, containing two Ultra and a Hyper Secret Rare Pikachu & Zekrom GX.
Likely released soon after this set in February 2019, we also had the Portuguese SM168 Pikachu & Zekrom GX Full Art promo, released inside the Tag Team Tin.
Next we have the Detective Pikachu mini set, which as its name suggests contained a Holofoil Detective Pikachu card. This mini set is likely released on April 5th, 2019, despite the lack of sources, since most of the sets are released on the same day as their English counterparts during this era based on the other sets for which we do have sources available (now).
Then we had the Portuguese Unbroken Bonds set of May 3rd, 2019 (source1; source2), which again contained a non-Holo and Reverse Holo Pikachu.
On May 9th, 2019 (source) we had the Portuguese Holofoil SM190 Detective Pikachu promo, released to celebrate the cinematic release of the Detective Pikachu movie.
Followed by the Portuguese Unified Minds set, released on August 2nd, 2019 (source1; source2). This set contained not one, but two Pikachu.
Then the Hidden Fates set of August 23rd, 2019 (source), which included a Pikachu as well.
The final Portuguese set of the SM era was Cosmic Eclipse of November 1st, 2019 (source1; source2), which contained both a regular and Character Ultra Rare Pikachu.
Released somewhere in November/December 2019 we also had the release of the Portuguese Pikachu GX & Eevee GX Special Collection box, containing the SM232 Full Art Pikachu GX promo in both regular and Jumbo size (the first Portuguese Jumbo Pikachu card), as well as the Holofoil SM234 Pikachu promo and two Eevee promos.
Next we have the Sword & Shield era, starting with the set by the same name on February 7th, 2020 (source), which contained a Pikachu card.
Next we have two Portuguese Sword & Shield era sets lacking Pikachu cards:
- Rebel Clash, likely released on May 1st, 2020 (lacking sources);
- Darkness Ablaze, released on August 14th, 2020 (source).
On August 14th, 2020, accompanying the Darkness Ablaze set, we also had the four Darkness Ablaze Blisters, one of which contained the Holofoil SWSH039 Pikachu promo.
Next, likely released on September 25th, 2020, we had the Champion’s Path set, lacking any Reverse Holos.
Then, somewhere in September/October 2020, we had the Portuguese V Power Tins, including a Full Art Pikachu V promo with number SWSH063.
Followed by a personal favorite set of mine (not!.. 
), the Portuguese Vivid Voltage of November 13th, 2020 (source), containing three Pikachu V/Vmax Ultra Rares and a Hyper Secret Rare Pikachu Vmax.
And the final Portuguese Sword & Shield era set (likely) released before February 27th, 2021 is Shining Fates of February 19th, 2021, lacking any Pikachu cards.
But of course we have two more Portuguese Base Set artwork reprints released slightly after this February 27th, 2021 boundary date.
First of all, the Jumbo Base Set reprint for the 25th anniversary, likely released in late February or early March, 2021. Unlike this same Base Set Pikachu Jumbo reprint in other languages, the 25th anniversary logo is always non-Holo on this Portuguese card.
And lastly, the full art Base Set reprint, of the Celebrations set of October 8th, 2021 (source).
And there you have it, all Portuguese Pikachu cards and set releases. And again, huge thanks to my Brazilian middleman Francis, since without him I might not have all Portuguese Pikachu (and Seviper) cards by now. 
Greetz,
Quuador