Unlock V-Hard Mode:
On 1-Player Stadium go to the difficulty selection screen and hold the Z button and press L, L, A, B.

Unlock S-Hard Mode:
On 1-Player Stadium go to the difficulty selection screen and hold the Z button and press R, L, A, B.

Start From Level 50-99 in Marthon Mode:
At the Title screen hold Z and press B, A, L, L. You will hear a sound if the code has been entered correctly.

Unlock ALL Puzzles in Puzzle University:
At the Title screen hold Z and press A, B, R, A, A, B, R, A. You will hear a sound if the code has been entered correctly.