Most BMX have sprockets with freewheels as one unit. This means that you need a special puller to grip notches on the freewheel to be able to unscrew the old one. The new one can be started by hand and will tighten down by itself as you pedal. If you have a low-end one with a built-in coaster brake other rules apply and you're probably looking at something with a lockring arrangement.
They are designed for 2 different riding types. If you have the ability the modify a steel, steel composite, or aluminum frame you can do it. But there is a urban sport type of bike out there called a 29er bike.
You can use a MTB any way you want. but being bigger it will also be heavier, more cumbersome and more likely to break if it gets tossed around. In short track racing, tricks and jumps it'll be much harder to handle than a BMX. OTOH it'll go faster and be better for distance riding.
Probably not. BMX bikes usually have freewheels while MTBs usually have freehubs, and these don't mix. You might be able to use parts from a single-speed MTB on a BMX though.
No simple answer to that. Both BMX and MTBs have several different types of bottom brackets. Some of these are interchangeable, some aren't.
Depends. There are several different sizes of steerer tubes, stems and bars. Some will work together, others won't. Depending on what parts you have, you may well succeed.
It´s the Stem, it holds the bars and match with the frame with the help of a headset.
put my mum on the seat and grind
Change the wheels with specil ski wheels i think its called ski bike.
axle mounted, yes.
A 20 inch tire.
Yes, pegs can be put on any BMX Bike. You will need a socket wrench to put pegs on certain bikes how ever.
Too many steps to answer here, go to www.parktool.com, www.sheldonbrown.com or www.bicycletutor.com for more.
Depends on what's already on there, what's available, and how much clearance the bike has at the fork and frame.
u could cut it up then make all the bits smaller and then put weld it back together again
Not a sprocket only, but you can buy a 23-tooth freewheel that should fit.
It is not very hard to put full downhill on a normal mountain bike but you need to take it to a professional.