Must a person who disbelieved and then returned to Islam perform ghusl and utter the two testimonies as one who embraces Islam for the first time, and will Allah accept his repentance?

The repentance of an apostate is by uttering the Two Testimonies (Shahadatayn). If he prays, his Islam is affirmed because prayer includes the Two Testimonies. However, if his apostasy was due to denying an obligatory act (fard) or similar, his repentance is by uttering the Two Testimonies along with affirming what he had denied. The ritual bath (ghusl) for an apostate is not a condition for the validity of his repentance.