Even in Connecticut, which passed some of the nation’s toughest gun laws in the wake of the Sandy Hook shootings, anyone could get a ready-to-assemble gun by mail.
You can order a rifle kit all you want, but it has to be mailed to an FFL dealer in every state. You can get an 80% receiver which is FAR from ready to assemble, so yes everything the idiot says is total BS.
No, it does not. As long as the rifle kit, like the one from CDNN Sports that I linked to, does not include the registered piece (lower receiver in the case of an AR), it can be shipped to your door as long as the resulting firearm is legal in your state.
The AR lower receiver must be transferred by an FFL unless purchased face-to-face with another individual in your state, again given that such sales are legal in your state.