It is called a pistol
Pistol aficionados refer to it as recoil.
The case that the pistol is stored in is simply referred to as a case or if you have a case that you can more easily carry with you but that also secures the gun and is easily accessible, that is a holster. The outer shell of bullets are sometimes referred to as casings.
Case length, case capacity, bullet diameter
It is called a grip.
May be called a "stovepipe", since the empty case is frequently caught pointing up, like a miniature stove pipe.
It is called the Mossberg 45 Pistol.
Well, there were swords with built in pistols called a Cutlass pistol, there are pocket knives with a single shot pistol, called a knife pistol, and military rifles with a bayonet on them (no special name).
A gunsmith
A pistol
A case, scabbard, or in slang terms, a "gun rug" for a padded pistol case.
You probably have a Mk. I pistol, manufactured circa 1958. If this is the case, it would be a semi-auto pistol, chambered in .22 Long Rifle.