It isn't generally illegal to carry on a boat, assuming you can otherwise legally carry a handgun, however, it may be illegal in certain locations. If you are on a federally controlled waterway, it is probably illegal, or some states may have restrictions.
Added: Check the laws of your particular state. The same law applies to boats as would apply to motor vehicles on state waterways. See above answer for the answer to federally controlled waters.
All countries - once you have legal permission, allow you to carry a handgun.
Only if you have a legal license
The same laws apply to boats as apply to vehicles.
It depends on what you mean. If you legally possess the handgun, then it is legal to have it in Tennessee. Tennessee doesn't require any kind of registration, however, you do have to have a valid handgun carry permit to legally carry it on your person or have it accessible in your vehicle.
In the U.S. you have to be 21 in most states to get a handgun carry permit.
No. It is also a very bad idea.
If you have a handgun carry permit, definitely. The handgun carry permit covers "any handgun that you legally own or posses."
No. As of 2010, Arizona allows anyone who can legally own a handgun to carry it, openly or concealed, without a permit. Before then, you could carry openly without a permit, but not concealed.
Generally speaking, yes. Some companies have policies against carrying a handgun on company property, including company owned vehicles, but as far as actually against the law, it is legal, as far as I know, in all states, *IF* you can legally carry a gun in public (some states require a permit), and the state of Illinois currently doesn't allow carry of a handgun in public at all.
Not sure what you're asking, but I'll take a stab at it. If you're asking "Is it illegal to carry a handgun," the answer is, it depends on where you are. In the U.S. some states require a permit to carry a handgun concealed, but a few don't. A few states allow you to carry a handgun openly, but most don't. Two states, Wisconsin, and Illinois, and D.C. don't issue carry permits.
It depends on where you are. In the U.S. each state sets its own rules. For instance, in Tennessee, there is no such thing as a weapons permit, it's a handgun carry permit, and applies to handguns only. Other than handguns, basically anyone can carry any legal weapon, but to carry a handgun, you must have the handgun permit. On the other hand, Florida issues a "concealed weapons permit" and it covers any legal weapon.
In most U.S. states, there is no specific minimum age to use a gun for legal purposes, but a person does have to be 21 to legally own or purchase a handgun.