Codes:

 Level 1 (Prison): ZARTACLA
 Level 2 (Hotel): RINGMYBEL
 Level 3 (Kitchen): SCRAMBLED
 Level 4 (Hospital): ANASTHETIC
 Level 5 (Penthouse): ETAGSLLEH

Cheats:

 Level Select     KRISTIAN
 God Mode         PILCHARD

How to get to the bonus level:

 At the beginning of the first level you start at the wall.  Go to
 the right side of the wall (where it stops) and then jump up while
 holding the pad to the left. You will jump onto a secret walkway.
 Walk to the left and jump up again. You will come in the bonus level.
 Losing life in the bonus level does not effect your lives in the game
 so collect as much as you can get. When you have 1000 musicnotes
 collected you will get a extra live!.

 Taken from Cheet Sheets 53 by Wayne Roberts