Peter was abolutely saved!
There are the terms "Peter's Gospel" and "Paul's Gospel" out there in Christendom. What is going on here? Are these really differences without a true distinction? Are Christians just making this stuff up?
The Apostle Peter held on to the Judaic Law requirements of circumcision for new Gentile converts. He did this because of pressure put on him by the other Jews who were in the church who believed that Jesus was the Messiah. Remember that 99% of the early church was made-up of Jews, along with a few Greek prosylites.
Jesus Christ Himself did pick Paul (formerly Saul) to be the Apostle to the Gentiles. The "mystery" which was revealed to Paul and Paul alone was that before the foundation of the world God had the Church in mind. God already planned that His Son's sacrifice would be sufficient to reconcile the whole world back to Him, by the finished work of Christ on the cross. This is a grace-based faith dependent on what Christ did. Judaism required man's works, such as circumcision. Paul argued to the early Church that God was no longer requiring circumcision, especially of the Greeks/Gentiles.
If you look at Galations 2:11 you will see that Paul got toe-to-toe with Peter and rebuked him for false teaching and siding with those who wanted to enforce the requirements of Judaism on the new converts.
The Peter we later see in his own epistles is a person about thirty-five years after the events recorded in Acts. Peter, in his epistles, did admit that Paul's teachings did have authority (if hard to understand) and he approved of Paul's teachings.
Galatians 2:11 But when Cephas came to Antioch, I opposed him to his face, because he stood condemned.
2Peter 3:15 And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him,
2Peter 3:16 as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures.