Paul didn’t need to teach Peter, and we know that because he didn’t.
Gal 2:2 I went up because of a revelation and set before them (though privately before those who seemed influential) the gospel that I proclaim among the Gentiles,
in order to make sure I was not running or had not run in vain.
Paul wanted to confirm with the other apostles, likely including Peter, that he was teaching the true gospel. Paul is likely referring to Acts 15:
Act 15:2 And after Paul and Barnabas had no small dissension and debate with them, Paul and Barnabas and some of the others were appointed to go up to Jerusalem to the apostles and the elders about this question.
…
Act 15:7 And after there had been much debate, Peter stood up and said to them, “Brothers, you know that in the early days God made a choice among you, that by my mouth the Gentiles should hear the word of the gospel and believe.
Act 15:8 And God, who knows the heart, bore witness to them, by giving them the Holy Spirit just as he did to us,
Act 15:9 and he made no distinction between us and them, having cleansed their hearts by faith.
Act 15:10 Now, therefore, why are you putting God to the test by placing a yoke on the neck of the disciples that neither our fathers nor we have been able to bear?
Act 15:11 But we believe that we will be saved through the grace of the Lord Jesus, just as they will.”
Peter had converted Gentiles before Paul ever did and confirmed that Gentiles and Jews “will be saved through the grace of the Lord Jesus.”
Neither are sent to me. They both died almost 2,000 years ago. Again, I think your idea of apostleship is incorrect. In no way whatsoever does it mean that we aren’t to follow the teachings of others besides Paul. God essentially put Paul in charge of bringing the gospel to the Gentiles and establish churches, to ensure the work would get done. It does not at all mean that Gentiles are to only follow Paul.
We know this because Paul says that “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work.” More than that, Paul himself also says:
1Co 1:12 What I mean is that each one of you says, “I follow Paul,” or “I follow Apollos,” or “I follow Cephas,” or “I follow Christ.”
1Co 1:13 Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?
That really should end the discussion.