At the main menu, press L1, L2, R2, R1.
At the main menu, press R1, R2, L2, L1.
Pause the game and press Triangle, Up, Circle, Right, Select, Square.
Pause the game and press Left, Right, Left, Right, Square.
Pause the game and press Left, Right, Up, Down, Circle, Square.
Pause the game and press Left, Right, Left, Right, Circle.
Pause the game and press Circle, Square, L1, L2, R1, Select.
Pause the game and press Down, Triangle, Select, L1, R1, Select.
Pause the game and press R1, L1, R2, L2, Left, Right, Up, Down.
Pause the game and press Square, Circle, Triangle, Select, Left.
Pause the game and press Triangle, Square, Circle, Triangle, Circle.
You must play the game on the "Hard" difficulty setting to completely finish the game.