Cheat Menu:
At the Main Menu with the Start, Options, and Credits options, press Lx3 R R L L Rx3 L R and a Cheat option will appear.
Color Change:
To change the color of your fighter, choose it by pressing Y+X+B+A on the Character Selection screen.
Ending:
Make sure to have the Difficulty set at 10 and Gore set at Y if you wish to see the Ending after beating the game in the 1-player mode.