At the title screen, press Up, Right 9 times, Down 6 times, Left 7 times, Z, X, Y, Y, Y, Z
999 lives
Enter the Level Select Code, then press: Left, Right, Right, Up, Right, Right, Up, Down, Right, Right, Up, R. The "Last Boss" will now be on the list.
Enable the Final Boss Stage
At the title screen press Left, Up, Right, Down, Down, Right, Right, Up, R. Press Up or Down to select your starting level.
Level Select