2-"PHO" | 3-"MET" | 4-"BLA" | 5-"SUP" | 6-"TRA" | 7-"QUA" | 8-"NEO"
These next two are just guesses (the level codes for the CD32 are the same as the first three letters of the A500 version, so the cheats may also work):
Try entering "MEC" for your password for infinite lives.
Try entering "BIG" for your password to see the ending.