First, check the game laws of YOUR state- they vary from state to state on what is a LEGAL weapon. I live in Virginia- and .223 and 22-250 are too small HERE.
My personal view is that .243 and larger caliber are suitable for deer. 30-30, 7mm-08, 308, and 30-06 are the classic deer cartridges. There are others that also work well.
Any caliber can do the job. Most states regulate what can be used.
Yes- a very good deer rifle.
Winchester 94 in 30-30 caliber.
The term "squirrel gun" was used with muzzle loading rifles that were smaller caliber than deer rifles. There was no one set caliber, but many were in .32 caliber, where a deer rifle would be .50, .54 or larger.
.22 caliber pellet guns and .22 caliber firearms are intended for target shooting. The .22 firearms can be used for small game- rabbit and squirrel come to mind- but in most areas are NOT legal for big game- deer and similar animals.
If you are talking about a PCP (PreCharged Pneumatic) rifle. With a .45 caliber pellet, then "Yes" It can. I don't believe there is a 40 Caliber pellet gun.
$300-400
50-500 USD depending on specifics
Yes. There may be limits on the CALIBER, and PA does not permit semi-auto rifles for deer hunting, but other than that, the AR style rifle is nothing but a semiauto rifle.
It depends on what you mean. If you mean legally, many U.S. states require a caliber larger than .22 or 223, however, that IS legal in some states. If you mean what caliber will kill a deer, almost any rifle caliber will, but .22 or .223 is questionable, which is why many states prohibit that for deer hunting.
New York State does not have a caliber requirement for deer, except to say that rimfire rounds may not be used. A semi auto rifle used for deer hunting may not hold more than six rounds.
caliber limitations are set by the hunting ministry in your region, eg 243 for deer(smallest) 22lr for smll game eg rabbits and so on