To skip levels, hold down the 'A', 'R', 'M', 'I', and 'N' keys.
On level 3 stand at the end of the row of blocks and jump up to hit an invisible block; this will warp you to level 6.
BOMB = press and hold fire, move joy: up to Left Top diagonal to Right Bottom. Direction: ( \ )
CLOCK = press and hold fire, move joy: up to Right Top diagonal to Left Bottom. Direction: ( / )