Level Select
Enter options and select practice mode. In practice mode pause and enter B, A, B, A, RIGHT, A, C, UP, START. The screen should flash white. Next hold DOWN+A+B+C and press START. Now when you enter a normal game at the character select screen you can press UP and DOWN to select your level.
Map Mode
To view a map of the current level, pause the game and press B, A, B, A, RIGHT, A, C, UP, START.