Digital Champ

Sound test:
Press II, Select, Up, Run at the "New Game/Continue" screen.

Level select:
Press Up, Left, Down, Right, Run at the "New Game/Continue" screen.

View ending sequence:
Press Up, Up, Down, Down, Left, Right, Left, Run at the "New Game/Continue" screen.

Four screen mode:
Press Up, Right, Down, Left, Run at the "New Game/Continue" screen.