Can a sitting president just up and take Air Force One anywhere?

There's nothing to prevent him from doing it. We the people of the United States have given him that right. We can also very easily yank it away. Vote.

He has very rarely, as in almost never relatively speaking, used it for anything other than campaign rallies, nearly on daily basis from day one. He filed for re-election on his first or second day in office, and he has been doing nothing but campaigning and dividing since.

Airforce One is any aircraft that the potus flies in, regardless of type. Helicopter or fixed wing aeroplane.

Pretty much anywhere with a long enough runway to land it.

Nope. None have been to the North or South poles! 😈

This one can