ok ill start witht he first question...
you can have either a 3" or 4" lift, 4" is better if you plan on offroading but if you Are jsut gonna go on some easy dirt roads or some easy mudding you'll be fine with 3" of lift
yes you can use your stock wheels, but you wil ahve to either add spacers or put washers in or something to reduce the amount you can turn your wheels.
However i do not recommend this option, the best bet would be to get some steel wheels that are like $67 each in 15X8 and 3.75 or 4 backspacing
bedgetboost lifts are primeraly 2" lifts, they put a spacer on top of your coil and usually come with new longer shocks, these are good if you ahve a newer jeep that's coils stil ahve a good ride and havent sagged
SUspension lifts are new longer coils and longer shocks and if you get into big suspension lifts they come with other components that help with the driveline geometry
a body lift just lifts the body off the frame and hte biggest one you should get is a 1.25 in BL (they are spacers taht go between teh fram adn body mounts