I don't think he's referring to the passwords you have to give other mudokons in Abe's Oddysee, he said it's Oddworld Adventures which is the gameboy advance Oddworld game (I think).
So I imagine by passwords he means like the alternative to game-saves, passwords where you get given a password for each level and you can use that to skip straight to that level next time you start. But what he's saying is that there are several different passwords for one level so it's possible that there's secrets in the preceding level that result in that password.
Or at least that's my impression of what he's trying to say
As for your actual question, Marlz, I don't actually have Oddworld Adventures so I can't help you there, but hopefully some other people may be able to help.