My first quad and many questions!

Hello everyone! I will be 17 years old (young) in 2 days and would like to make a quad driver’s license now. Actually I could also make a car driver’s license, but it is currently too expensive for me as a student. This is then my first, own vehicle. As you can probably imagine I have 0 idea of the technical data, etc. of a vehicle, since it has never interested me until now and never needed it. I have already read some threads here, but I would like to please let experts advise you extra 😉 Please don’t laugh at my following questions, because I’m really just a layman. ( But actually I don’t care, laugh calmly ;-D ) Would be nice if you could explain some things to me. One thing is clear to me: I can only drive 50ccm quads, but that’s enough for the time being! 1. Is there a big difference between 2 and 4 bar quads? And what is the bar actually? 2. My father thinks I need one with differentials, is that really so wi Is that possible at all? 4. What do the cylinders matter? I mean, what is the difference between 1 or 2 cylinders? Since the driver’s license is limited to 50ccm quads, I want at least a powerful part, which plays in the upper 50ccm class! Can I recommend something or what do I have to pay attention to in order not to get a “lahms part”? Could you possibly also give me a few mars? ken recommend, since I have heard that the China Quads are absolute? Thanks already for your answers, mfg