There are variations on the Phantom 3.
The standard - still available I think - uses a fairly simple wifi link and even under ideal conditions don't expect it to go much more than 1500 feet.
That's often enough though.
The earlier Pro and Advanced had a more advanced radio link and the limit was more the battery life than radio connection.(i.e. 2 miles or more)

The point about compatible firmware on controller, drone and phone app still holds true whichever one it is.
The app will update itself unless auto-update is turned off.Then you can be railroaded into updating everything when there was no need but all latest should e fine anyway.

If it hasn't been used for a while simple things can be overlooked such as keeping the antennas parallel and with the sides not the ends directed towards it.