It's quite simple, the caracter is part of the code and the number shows the positon of that caracter in the code.

I think some of em won't get released until Phase 2 of the event

i can't see any of the mentioned or imma too much boomer to notice

O4-at the banner when you choose quest

Note: the devs lied about them all being inside the game.

K2-main page rotating banner

is the T5 in the ultimate level quest title part of the code?