Erase a Saved Game - To erase a saved game file, highlight the file you wish to delete and press the following:

Code Effect - Hold Select, press A + B Erase Game

Unlockables - Extra normal Levels

To unlock extra normal levels, do this:

Mario 5, 6, 7 Beat Mario's 1st 4 Levels.
Mario 8, 9, 10 Beat Mario's 5th, 6th, and 7th Levels.

Wario 5, 6, 7 Beat Wario's 1st 4 Levels.
Wario 8, 9, 10 Beat Wario's 5th, 6th, and 7th Levels.
Wario's Super Picross (Wario 1, 2, 3, 4) Beat Mario's 1st Level.