At the main menu press the following to enable cheat funcation.

Level Select: 
Triangle, Circle, Triangle, Square, Triangle, Circle, L1 + R1. 
 
Unlock All Costumes: 
Triangle, Circle, Triangle, Square, Square, Square, L1 + L2. 
 
Unlock Debug Menu 
Triangle, Triangle, Circle, Circle, Square, Square, Circle, Circle, L1+ R1 + L2 + R2. 
NOTE: The Debug menu will be available from the pause screen. 
 
Unlock all Cerebro Files 
Triangle, Circle, Triangle, Square, Square, Square, R1 + R2.