Harder Game
When the Title Screen appears, hold L + R, then press Start. Go
to the Options Menu to discover a new difficulty setting "Very
Hard."
Level Select
Choose Music on the Option Screen. Set the music number to the
number of the stage you wish
to play, then hold Select while pressing L, R, R, L, Start. After
a few seconds, you'll warp directly to the level of your choice.
To select a bonus stage, select "HIT" for your music.
To play against a boss, select "BOSS."