There are two different hub designs for BMX, freewheels and freehubs. You need to know what you have if you want to replace the sprocket by the rear wheel.
It's not really a question of better, more of different. What decides how fast the top speed of the bike is, and how nippy it is off the start is the ratio between the tooth count of the crankset, and the tooth count of the freewheel. With a smaller freewheel you can have a smaller crankset, a slightly lighter bike and get the same feel of the bike as with a bigger crankset and a bigger freewheel.
Of course it will, but in my opinion freewheels arent the best
If you have a flip-flop BMX hub, you can put a 14T on the smaller diameter side of the hub. If you have a cassette hub, you can get as small as 11T.
you would need a cassette. it would have to be 10 tooth
I'm assuming you're asking about how to remove the freewheel, as the Mongoose Rebel 20 is a single-gear BMX. In that case you need the correct freewheel puller to get the freewheel off. Check out www.parktools.com for more info.
I don't really know what you're calling a driver, but it's probably the sprocket and the freewheel mechanism. And yes, it can be removed. You need a special tool, a freewheel puller, and it has to match the make of the freewheel that you have. check out www.parktool.com for more info.
Unless by freewheel you mean driver (in which case 8-9) I haven't ridden bmx in a few years but last time I checked the smallest freewheel you could buy was 12 tooth which would make for quite a low ratio
Not a sprocket only, but you can buy a 23-tooth freewheel that should fit.
No. a 9T sprocket will only fit a cassette hub, and not freewheel hubs.
possibly, if you have the kind of hub where its solid and you can put on a single piece freewheel than no. But if you have the kinde where you need the single piece freewheel and a bolt to hold it on that yes. what you do is spin the thing that holds it on off and screw your nine piece driver it.
you need a freewheel remover. but if you don't want the freewheel anymore a vise also works too but don't clamp it down to hard just get it snug then spin the wheel so it spins off the freewheel cause some bike shops charge like 2-5 bucks to take it off
The only thing I can think of that would make a sound on a regular BMX would be the ticking from the pawls in the freewheel/freehub mechanism - the one way clutch that allows you to keep the pedals still while rolling forward.