Actually, I have gone hunting with a Thompson Contender (single shot, changable barrels) with a 10" barrel, 41magnum, with a 4x scope. Took a deer down with almost no problem. Lean against a tree for a little more support and dropped it in its tracks.
Some people prefer a revolver over an automatic. I have a friend who has trouble with the auto because they flinch when they see the round being ejected. Luckily, I've never had this problem. I also carry a Walther P-38 9mm, and I can put 7 out of 8 shots in the head of a target on a consistent basis, but that comes from lots of practice.
Now, with that out of the way, some hunters like using a .30-.30 rifle for a brush gun. Slightly less powerful round, but it will go through brush and low hanging limbs with less deflection because it's moving a little slower than a .30-06 round.
Other people I know like using the 7.62mm round (.308 Winchester) to hunt with because it does hit with a larger impact and the rounds are fairly easy to come by. Lots of manufacturers make rifles like this because 7.62 is (was?) the NATO standard round although the 5.56mm round (.223 caliber) is what the U.S. uses (The AR-15 is a popular civilian version of the M-16/M-4 carbine).
Also, depending on what you're hunting, a 12-gauge shotgun is easy to use once you get used to the kick. Some go hunting larger game with 12 gauge slugs while others swear by 12 gauge buckshot . . . some even come in a 12 gauge magnum version (little more powder behind the shot).
1. What kind if rifle would he use to hunt with that would be profficient for basically all purposes ie killing animals and people if need be?
I would say the .30-06 or a 7.62 rifle would make a great hunting rifle. Of course, if he's a treasure hunter and is expecting trouble out in the boonies where he's unlikely to run into the cops, he might have a sawed-off rifle (trim the barrel down to just sticking out beyond the foregrip and cut the stock off behind the hand guard) slung over his shoulder for carrying in and out of tight spaces. Obviously it'll be less accurate with a shorter barrel, but if he's shooting at something within 100 feet, a shorter barrel might be better.
Otherwise, he'd probably carry a handgun for self-defense (10mm, .40 caliber, .45 caliber would be most likely.)
2. If you are able to use a handgun and a rifle does that mean that you will be able to use any gun or rifle?
Yes and no. I trained on the M-16 in the Army. Could I pick up and use an M-14 or a G-3 or an AK-47. Sure, the basic function is the same. (Insert the magazine, rack a round into place, selector switch from safe to fire, squeeze the trigger.)
Would I be as accurate with any of them as I was with an M-16? Probably not. Each weapon has its own peculiarities, they weigh differently, sights are different, rounds are slightly different. Given time and enough ammo, I could certainly famliarize myself with the weapon, but yes, I could pick one up and spray lead at a bad guy or a charging wild boar. *grin*
Same with a hand gun. A Colt Python .357, a Ruger Redhawk .44 Magnum and a S&W .32 snubnose are all revolvers. Still, each one is going to kick differently, each one likely has a different trigger weight (they fire at different times as you pull the trigger back) and each weighs a different amount. All of these things will affect accuracy initially.
But, these are my opinions. Others may disagree.