If you are referring to a Sturm & Ruger Co. Mini-14, then the answer is that most were manufactured in .223 Remington. The Ruger factory has from time to time released the Mini-14 rifle in .222 Remington in limited numbers, most likely to satisfy limited markets (some countries do not allow sales of "military" calibers.)
your rg model 14 was manufactured in the 1960's.
15-50 USD.
No published sn data.
No published sn data that I am aware of. Best guess is 60-68
No published sn data. 25-50 or so
RG model RG31 Caliber 32 long manufactured by RG industries, Miami Florida
25-75
John Hinckley used a .22 caliber revolver to shoot President Ronald Reagan.
Best left to a gunsmith
No published sn data.
20-60 or so
No published sn data.