Yes, but there ARE restrictions on WHICH rifles, as well as which features are permissible.
Yes, no, maybe. You fail to mention how old you are and where you are located, both of which determine which answer is correct.
For a semiautomatic rifle, you must be 18. For a TRUE assault rifle, which is capable of burst or full auto fire, you must be 21. Federal law.
There are semiautomatic versions of the Tommy gun (Thompson sub-machine gun). They are legal to own. A fully automatic Tommy gun is legal in Texas only if you have the federal license.
You need to tell us which rifle. Chances are that there is some legal way to own it.
California has strict gun laws and I doubt that you can legally own a 20MM rifle in California. Usually the only guns available in California are small handguns.
Depends on where you are.
Chinchillas are legal to own as a pet in California.
Yes
Well, that depends on the laws where you live. In most of the US, they're perfectly legal, with the one exception being California. In other countries, the laws are much different.
no if he has a permit
Depends on the laws where you live.
Laws on this vary by country.