What's the difference symptom wise, of carpel tunnel syndrome and median nerve injury? Can cervical rf procedure cause median nerve injury?

No. Median nerve doesn't exist until your arm pit. It doesn't start in the neck. It is formed by the combination of two nerves about six inches away from neck where rf would be performed. Carpal tunnel syndrome speaks to injury of the nerve at the wrist.
Definitions. Quite unlikely, that cervical rf can cause median nerve injury. The median nerve can be injured at several sites in the arm, as can be compressed at anterior elbow, pronator syndrome, mid forearm, anterior interosseous syndrome, and wrist, carpal tunnel syndrome (however, on occasion, the carpal tunnel issues are more distal, in center of palm).
Median nerve injury. A median nerve injury at the carpal tunnel site should cause numbness in the thumb, index, and middle fingers. It may cause weakness of moving the thumb straight up from the hand. A median nerve injury higher in the arm could cause other symptoms, like turning a door knob, turning the palm downwards, or flexing the fingers into a fist / gripping with the fingers.