St. Peter was the one who brought in the first Gentile and proposed, at the Jerusalem Council, doing away with the Mosaic dietetic and ceremonial law. When St. criticized his habits, that was because S.t Peter's habits were out of synch with Peter's own understanging of the universality of the Church.
When did he become pope ?
One event in the scripture that points to Peter's actual assuming of the papacy is the "feed my lambs" passage at the end of the gospel of John.
He was part of the reason that council was called read Galatians ..
So he was pope before he had the Holy Spirit and before the church was born?? He did not think so He believed he was an elder..not even a priest