If symptoms in arm still persist after anterior distectomy with fusion and plates c7 t1 does it mean that there is irreversible nerve damage ?

Don't despair: The surgery may well have prevented further damage, but reversal of pre-existing problems may take time. Nerve damage may reverse, if optimal, at a speed of 0.1mm daily or speed of fingernail growth. Physical therapy has some potential, and exercise may restore part of this. An EMG test can tell if there is re-innervation and peripheral nerve sprouting.