I noticed that V4 and V5 use the same partner cable. Can the V4 controller be used with the V5 to control the robot?
No. There is a lot more to consider than just the fact that the connecting wire is the same (communication protocol, electrical properties, etc.).
Please also search to see if your question has already been answered before posting:
https://vexforum.com/t/easyc-registration/16563/1