To unlock Four Screen Mode, insert the following code at the start screen: Up, Right, Down, Left, Run.
In-Game Music
To unlock an in-game sound test that lets you listen to all of the game’s music, insert the following code at the start screen: II, Select, Up, Run.
Stage Selection
To unlock a level select option, insert the following code at the start screen: Up, Left, Down, Right, Run.
View Ending
To see the game’s ending automatically without actually having to beat the game, insert the following code at the start screen: Up, Up, Down, Down, Left, Right, Left, Run.