Not if its not designed that way.
It has to be electric (AEG).
No. Spring must be cocked before each shot.
You kan make 1
There are too many types: airguns that are used in the auto industry, Air Rifles, Air pistols, Air soft guns.
You need both.
Yes it is possible
No, only with a few Marui selected models, or with airsoft guns that have a threaded barrel of the same size.
A spring, an electric motor or by compressed gas.
No. it has to be cocked each time.
No. Wrong size.
new spring or check your compression.
No, not if it's designed to do so.