Go to a terminal while playing the game, then replace the disc with any other PlayStation 2 game. Exit the terminal, wait for the debug screen to appear, then replace the game disc.
Successfully complete the game, then start another game with your cleared game save. You will be able to replay the game with the Demonic Compendium, the ability to change costumes, and no level limit on fusions and summons. Press Select to toggle between first person and third person view.
Hold L1 + R1 and move the Left Analog-stick Left or Left Analog-stick Right and your character will sidestep. By moving the Left Analog-Stick Away, your character moves away with his back turned to the camera. Note: This does not work at places where you cannot rotate the camera with L1 or R1.