There's so much wrong there, I'm not even sure where to start.
Maybe start by reading your own Tanach?
The High Priest was anointed to his position, and called Messiah. Exodus 28:41
The King was anointed to that position, and called Messiah. 1Samuel 2:10
Is all Israel called anointed? Yes! But that in no way invalidates the title as belonging to the King and High Priest.
As for "another gospel," such thing surely existed, but such was the work of Cerinthus and Simon; not Peter and John. It was Peter's confession that "thou art the Christ" before ever Saul rode out to Damascus.
Jarrod
Don't forget that the gospels and Acts of the Apostles were written from 30 to 90 years after the Letters of Paul. And not a single book of the NT was written by a Jew. Jews would not write against their own Faith which was Judaism. They were all Hellenists former disciples of Paul.
If you want to know who were preaching the other gospel different from Paul's don't go after extra NT literature. Paul himself revealed them according II Cor. 11:4-6, 13. He was talking about the very apostles of Jesus with a gospel that he was ready to curse for being different from his gospel. (Gal. 1:6-9)
Regarding the anointed ones to be called Messiah, they were not. They were all Messianic leaders. The true Messiah is the one spoken of by Prophet Habakkuk 3:13. "The Lord goes forth to save His People
to save his anointed one." That's the real Messiah; the anointed one of the Lord aka Israel as the People of the Lord.
The King was anointed all right but as a Messianic leader within being a king. Even Cyrus was called an anointed one by Prophet Isaiah but in the sense of a Messianic leader for having freed the Jews from exile and financed the rebuilding of the Temple. (Isa. 45:1)