Expert mode:
Hold Select at the title screen until the word "Hard" is displayed.
Level select (Japanese version):
Press Select three times, then hold Left and press Run
when the house and lightning are displayed on the title screen.
Note: To face the final Boss, select level 0.
Level select:
Hold Run and press Select three times when the house and
lightning are displayed on the title screen. Then hold
Down/Left and press I. Note: To face the final Boss, select level 0.
Sound test:
Enable the "Level select" code. Then, press Select at
the level selection screen.