While playing, press RS, RS, LS, A, C, B, Right, Left, LS, then hold X to enter cheat mode. If you entered the code correctly, a door will appear in the upper left-hand corner of your screen. To use this code, continue to hold X and press one of the buttons below.

Button Effect

A Increase Defense
B Increase Offense
C Increase Agility
LS Toggle Invincibility
RS Increase rank