Is it ok to unsolder an outdoor spigot and to solder back a new one without cutting the copper pipe?
It's not mentioned in instructions because a professional wouldn't do it that way if they had a choice.


You need to get the water out of the line to heat it enough to melt the solder. That's easy enough when the pipe has been cut apart, but less so when you open the valve several inches away.
While heating, the pipe will get soft and you risk deforming it if you apply lots of torque to remove the fixture.
To apply the torque, you'll need some pliers since the pipe will be very hot from the blow torch. Trying to juggle pliers, a blow torch, and a very hot fixture with melting solder coming off of it is asking for trouble.
Once removed, you need to clean the threads of any solder and corrosion to be usable again.


That last part will take a lot of time to do right. In the interest of time, and to do the job right, professionals will cut the pipe a short distance back and replace it with new pipe. As a favor to the next person behind you, I'd recommend using pipe dope on the threaded connection rather than solder. This way the fixture can simply be unscrewed and replaced without a blow torch and opening up the walls.