Yes, he is a successor to the apostle but he must still follow Church Tradition, i.e., there are councils which do delineate and require conformity, i.e., converts cannot be received into the Church wily nily:
The Ecumenical Councils, the Second and especially the Sixth, directed by their decisions, who should be received into Orthodoxy by means of baptism, who — by means of chrismation and who — by means of repentance, the repudiation of heresy and confession of the Orthodox Faith. By this it piously maintained the rule about the non-repetition of a valid baptism even if it was performed outside the Orthodox Church.
The 7th Canon of the second ecumenical council:
“Those heretics who come over to Orthodoxy and to the society of those who are saved we receive according to the prescribed rite and custom: we receive Arians, Macedonians, Novatianists who call themselves ‘pure and better,’ Quatrodecimans, otherwise known as Tetradites, as well as Appolinarians on condition that they offer libelli (i.e., recantations in writing) and anathematize every heresy that does not hold the same beliefs as the holy, catholic and apostolic Church of God, and then they should be marked with the seal, that is, anointed with chrism on the forehead, eyes, nostrils, mouth and ears. And as they are marked with the seal, we say, ‘seal of the gift of the Holy Spirit.’ As for Eunomians, however, who are baptized with a single immersion, Montanists, who are called Phrygians, and the Sabellians, who teach that Father and Son are the same person, and who commit other abominable things, and [those belonging to] any other heresies — for there are many of them here, especially among the people coming from the country of the Galatians, — all of them that want to adhere to Orthodoxy we are willing to accept as Greeks *. Accordingly, on the first day we make them Christians; on the second day, catechumens; then, on the third day, we exorcise them with the act of blowing thrice into their face and into their ears; and thus we do catechize them, and we make them tarry a while in the church and listen the Scriptures; and then we baptize them.”[27
There was a prescribed rite and custom upon receiving certain heretics into the fold of the Church, i.e., Arians, Macedonians, Quatrodecimans . . . etc., were chrismated, while others were baptized, i.e., the Sabellians, Montanists, and Eunomians.
p.s. I am using a Russian Orthodox source.