Various metals. Steel, polymer, or a combination of both is pretty common. Some really cheap guns are made from some sort of zinc or other cheap metals.
No.
Rifles, shotguns, handguns
Handguns and long guns.
Yes, they are.
Italy and USA
Italy
trainers are made from leather and silk
Rifles, shotguns, handguns, machine guns.
Rifles, shotguns, handguns, machine guns.
copper and silver
Wood
If you're asking when were handguns first made, the answer is the 1400s. The first handguns were basically small hand-cannons.