just making sure i am clear regarding unlocks.
1) activate trainer at main menu
2) enter the LOCKER ROOM
3) go ahead and enter the CUSTOM CLASS screen
4) note price of unlocking a custom class
5) back up to the LOCKER ROOM
6) press option key
7) go back into CUSTOM CLASS SCREEN
8) note price of unlocking is $0
9) UNLOCK THEM ALL!
i hope this is more clear.
If there is other unlocks in the game, maybe i missed them.
Also, if this doesn't work for you then I am not sure how else to address it, since I can repeatably do this over and over using the trainer.
The trainer was deliberately designed not to work in multiplayer. Cheat Happens does not support multiplayer cheating.