Can I return to my old job after removal of a ganglion cyst?

Usually. After an appropriate recovery time return to work can be expected .
Yes. A lot depends on what your job is, but yes one can usually return to prior work unless it involves strenuous wrist activity. In that case a little rehab may be in order.
Yes. Yes eventually. Dep on location and size of cyst and occupation. Once healed there are no restrictions.