Yes, if you can find the correct bottom bracket for the frame.
BB usually stands for Bottom Bracket, the part which holds the cranks/pedals to the bike
It will if you have bmx (or bmx style) cranks.
take the cranks off and then take your old sprocket off and then put the new one on and then put the cranks back on.
Five. One for each wheel, one for the cranks and one for each pedal.
It'd be a fairly strange BMX if it has a gear shaft. Most "real" BMXes are single speed, their driveline consists of cranks, a bottom bracket and the rear hub. No gear shaft there.
Go to bike shop or wolyworld and buy a link remover.
you can find a BMX bike in halfords
The bmx thruster rampage bike is a exellent bike
The advantages of using 160mm BMX cranks include improved ground clearance, reduced pedal strikes, and better maneuverability for tricks and jumps.
One can buy a custom BMX bike in Las Vegas from a few stores. One can get a BMX custom made from 'Just BMX', 'Bolder BMX', 'Bike World' and 'Vegas Bike Store'.
it is easier to pedal with longer cranks because you have more leverage but it is not necessarily better to have really long cranks.