Yes, it is legal. Florida has no AWB in effect. However, anything you add must be US made.
We can't answer that. It oes not violate US Federal law, but SOME states have their own laws, and you did not share what state you are in. A good start would be to check with the State Police or a gun dealer in your state.
No, it is not legal.
Yes, provided the magazine has not been modified to accept more than five rounds or the shotgun has not been modified to accept a detachable magazine, and it does not have a collapsible buttstock or pronounced pistol grip.
You must be 18 to buy a rifle. The stock has nothing to do with it.
If it's illegal with the magazine, it's every bit as illegal without the magazine. Assuming you're referring to a semi-automatic handgun, the type is perfectly legal in Florida, and it's perfectly legal to transport one to the state, so long as your ownership of it is legal. You may want to contact the Florida State Police to ask how you should transport it while in the state of Florida.
I'm not sure how the system of purchasing a pistol in Florida works, but converting a rifle into something which the BATFE would class as a pistol without being able to legally own a pistol would be illegal, not just in Florida, but in the entire US. Now bear in mind that, to be classed as a pistol, it would have to have just the pistol grip, and no buttstock. If it's a combination of pistol grip and buttstock, it's still considered a rifle, and is still legal, so long as the rifle is still compliant with state laws. Some states (New York, New Jersey, California, Connecticut, Cook County Illinois) still have so-called assault weapons bans in effect.
No. To be legal, the receiver must be a type listed for prohibition by the California Department of "Justice", and it must either feature a "bullet button" (thus making it a fixed magazine rifle) or be featureless (no pistol grip, no collapsible buttstock, no forward grip, no flash suppressor, etc.).
Seagull vagina
Yes
yes butterflys are legal in Florida r u stupid
You need a lawyer for a correct, legal, and current answer.
In general, yes.