Depends.
If possible, it takes quite a bit of doing. External gear hubs are usually wider than internal gear hubs, so you'll probably need to respace the frame.
No big deal if it's a steel frame, not advisable for aluminium frames. Not possible for carbon fiber frames.
Buying a new rear wheel is probably least expensive, but it'd be possible to rebuild your old wheel with a new hub.
Then you'd need a shifter, a derailer, possibly an adapter claw to mount the derailer, and some cabling.
You need to figure out how to run & secure the cabling as your bike won't have the required brackets.
Or you'll have to track down several wraparound cable stops.
Realistically, you can expect to spend more on the conversion than what a new used bike with the desired properties would have cost you.
a track bike, or a bike with internal hub gears.
No. a 9T sprocket will only fit a cassette hub, and not freewheel hubs.
Probably. Today BMXes can have either a freewheel hub or a cassette hub, but as long as you stay within the hub type you can move parts from one bike to another.
A bike cassette is a stack of differently sized sprockets that are stuck on to the rear hub, giving the rider a range of gear ratios to choose from.
No because the bike would brake evry time so no
Yes. The road bikes and MTBs have multiple gears while the BMX and track bikes only have one.
it is a hub made by Primo bike co. it is designed where you can put in an 8 tooth driver, unlike most cassettes where you can only go as low as 9 tooth
If they're all inside the hub they're called internal gears, and consist of something mechanics refer to as "planetary" gears. If they are toothed discs that sit outside the hub they're called sprockets. The whole assembly is either a multi-speed freewheel. or a "cassette" for a freehub.
10-speed can mean two things these days. Either it's an old bike, with two chainrings up by the pedals and five sprockets on the rear hub. (2x5 = 10) Or it's a newer bike, with one chain ring and ten sprockets on the rear hub. Whichever it is, those are the gears.
this question doesn't make sense, because a "cassette-style hub" has a cassette, not a freewheel. if it's a cassette, surly sells a conversion that allows you to fix a cassette. if it's a freewheel, you can do it by threading on a track cog and a lockring. only problem is the lockring and cog are both threaded the same way, so if you break hard with the pedals there is a risk of the cog coming loose. A proper fixed-gear hub has a smaller, reverse threaded bit where the lockring attaches, solving this problem.
It drives the rear wheel. Used on newer/more expensive bikes instead of a freewheel.
If they're all inside the hub they're called internal gears, and consist of something mechanics refer to as "planetary" gears. If they are toothed discs that sit outside the hub they're called sprockets. The whole assembly is either a multi-speed freewheel. or a "cassette" for a freehub. It'd be very rare to find one of those with only 3 sprockets.