Press Up, Down, Left, Right, B(4), Start at the title screen.
Press Up(4), Down, Left, Right, Up, Start at the title screen.
Continue game play
Press A, B, Select, Start at the game over screen.
Solving the level 5 maze
Only enter the doors that are guarded by skeletons.
When Game Over appears on the screen, press the A button, then the B button, then Select, then Start. You will continue on the last board that you died on.