MK 1 in 9mm Parabellum and
MK2 in 7.65x17SR (.32 ACP).
It was silenced
One
Possibly the Welrod pistol, or the DeLisle carbine, both invented in Great Britain. However, a .22 rifle firing .22 Colibri ammunition is so quiet that you can hear the click of the firing pin.
Yes
You will have to tell us what you want to use it for.
.380 auto ammunition can be a "ball" style bullet or metal jacketed hollow point.
Fire ammunition.
.45 ACP means Automatic Colt Pistol. It IS .45 Auto.
Yes.
A pistol by loading ammunition into the chamber. The firing the pin then strikes the cartridge, which causes the pistol to discharge.
"Best" is a very slippery term. Among the quietest suppressed firearm was one made in Britain known as the DesLisle Carbine. Another was the Welrod pistol.
It is available if you look.