Debug mode:
Pause your game, the press and hold L2 an push Left, Up(2), Triangle, Right, Square, Left, Triangle, Up, Down, Right(2). You have now unlocked every level in the game.

Invincibility:
Pause your game, the press and hold L2 an push Right(2), Left, Triangle, X, Up, Circle, Left.

Unlimited Spirit Spells when acquired:
Pause your game, the press and hold R2 an push Left, Triangle, Left(2), Circle, Left, Triangle, Right, Circle, Up(2), Down.