Nothing infinite will stay infinite. Codes that increase things like money will work but it won't be infinite without the gameshark (in other words some codes will make your money 9999999, or so but...
no you must have a gameshark to use gameshark code because there is no other way to enter them into the console but if you get a gameshark then many codes come downloaded on them so you don't have to...
Look up the cheats, then start the game. Go to cheat list and the click either Gameshark or code. Type or paste the code into the small box then press OK.
u eat a french fry