The golden boarding pass campaign actually preceded the ANA Pokemon card campaign. Due to the success of the initial launch of the Pokemon Jet, which apparently ANA did not expect, they decided to continue the services of the Pokemon Jet and also launch this “Original Gold Boarding Pass” campaign.
These boarding passes were commemorative gifts, so they were not actual boarding passes which could be used while travelling.
To apply for these, you had to travel via ANA, domestically, collect two boarding pass stubs and mail them to the designated locations on the special application postcard, fill in the required information, affix a 50 yen stamp, and drop it into the mailbox.
Implementation period was: Saturday, July 18, 1998 to Saturday, October 31, 1998
Application deadline was: November 9, 1998 (Monday) Postmark valid on that day
I believe the applicants could not choose which boarding pass they received and it was at random. However, I do believe some blog posts stating that since you could keep applying multiple times, they probably had a list of which boarding pass you received and they made sure you got a different one. I cannot verify this claim but it is safe to say the gifts were random.
Cheers!