Medium size game like a fox or raccoon.
yes
squirrel
When you say Air Rifle you are referring to a pellet rifle not a firearm. At present there are no 300 Cal air rifle being made.
No it's not a requirement but it helps
yes
The Daisy Model 25 is designed for simple plinking and target shooting.
25-100 or so
It's not designed for any attachments
An Original model 25, Made by who. There are several air gun manufactures who make .22 caliber air rifles.
yes
Rifle
Both Shinsung and Sam Yang make a 50 caliber air rifle. The largest caliber Weinrauch makes is a .25 caliber.