When you're in the level do not use the warp, instead collect everything on the way down. At the bottom of the maze collect the gem before collecting the coin. When you collect the gem the following list cheat keys will be available:
'HELP'--Skip to next level. | 'W'--For fire weapon
'DEL'------Activate shield. | 'B'--------For bombs
'L'--------For extra lives. | 'E'-------For energy
'A'----All coins collected. | 'F'--Freeze monsters
Enter any of the following for your password:
"CHEATOFF"---------------Shuts the above cheat off
"REVEAL"--Reveals the locations of hidden passages
"TUTORIAL"-----------------------------------?????
"SONIC"------------------------Increase game speed
"NORMAL"---------------Revert back to normal speed
I've also heard that the password "CHEAT" is supposed to do something.
In one player mode enter "QSSIFS4UYLS2WGKUN3" for the password and you will be wisked away to level three with enough lives to complete the game with ease.