If I bought a phone from Best Buy could I take it to any Best Buy to return it

Yup. If you bought it in Vegas, you could return it in Kenosha if you wanted to. That's what I did Same thing if you bought it online... you can return it to any store.

Yes

Yes but you will have to go threw geek squad

Yes but the tax may be different so you may make money or owe a little...

I've done it

Manager discretion most likely but I don't see why not. Call the store.