You will have to me more specific. Do you mean any rifle that fires a 30 caliber projectile or 30/06 or 308?
No reference for a savillion rifle. If you mean civilian, same as for a military rifle- it will depend on the caliber and barrel. Military rifles in the US are made by civilian companies.
Your question is a bit ambiguous, so I'll go with the notion you're referring to the longest confirmed kill by a sniper. That was achieved with a rifle chambered in .338 Lapua Magnum.
Yes
Unknown.
Stevens.
Remington
Take the rifle to a gun shop so they can figure out what make, model and caliber rifle you have. There is no 84 caliber long rifle.
Springfield Armory
H&a
They were made in several calibers- will be marked on the barrel.
The .950 JD Jones is the largest sporting rifle caliber made.
WHICH rifle? There is more than one type made in this caliber.