Cheat Mode:
     Pause  the  game, and press X, Y, X, X, Y, Y, X, Y, X, X, Y and Y
to unlock Cheat Mode.

Dark Campaign
     At the Episode selection screen, press X, Y, Y, X, X, Y, X, Y.

God Mode and Complete Mission
     Pause gameplay and press X, Y, X, X, Y, Y, X, Y, X, X, Y, Y.