With this code, its kind of interesting. Just go to the 'vault' option, then go the 'ending 2' option, select a ending and you can then play in the ending. You can explore the area and even kill the ending characters! To exit the ending level, Press Start and select the exit option.

With this code, at the Main Menu, if you leave it on this screen after a while a demo will start. When it says Loading, hold the L3 for 3-4 seconds, then let go of L3. The loading screen should still be up when you let go of L3. A few seconds later, the demo will start & you will be able to control the character. (This may only work for 1-Player Demos)