they most certainly do work online,you just have to make sure your always going to be player one,or player 2,either that or you put a joker command on the codes so you can switch from p1 to p2...btw,please don't make me explain Joker commands.
The guy I just played was changing characters each fight. without disconnecting from me. First he was Ashra, then Hotaru. Also i heard the cheat does work online but the other person cant see the cheat, he sees you as SCORPION.