Can emg ncs tell the difference between neuropraxia and axonometesis, can it diagnose how long the nerve will take to fully recover?

Yes and no. Yes am EMG /ncs is used to differentiate neuropraxia and axonotmesis but the test itself cannot tell how long a lesion will take to recover. The physician performing the test can give the person an idea of how long an injury will take to heal and whether it is likely to heal based on the test results.