Sure, Jesus knew everything He told the disciples. The question is, did Paul know everything Jesus told His disciples? That Jesus was Paul's teacher (whatever that may mean) doesn't answer that question. (I've had many teachers. And I don't know even a small fraction of everything they have said to others.)
But you were not personally called by Jesus, to be the "Gentile Apostle", in the "time of the Gentiles'"
Jesus did not personally come to you and reveal the "Gospel of the Grace of God"..
But He did this for Paul.
Not for Peter.
'Not for Jude
Not for any other Apostle.
Peter who is not the "1st Pope" didnt even know that Gentiles could be SAVED, could be a part of the family of God, until ACTs 10., when God showed Him.
That is 8 yrs, after Acts 2:38, and Peter still didnt know that The CROSS was for EVERYONE., and that is about 10 yrs after Jesus is back in Heaven.
When Jesus said to the remaining Apostles, before He ascended.... "i have many things to tell you, but you are not able to bear/hear them now".
A.) Then, once in Heaven, Jesus Called Paul into the Ministry, as a "chosen Vessel"..
Why didn't he say...>"as another chosen vessel" or.. "one of the chosen like Peter"?
its because what Jesus did with the original 11, was mostly for the House of Israel.. before the Cross was Raised.
And After the Cross was raised, the Body of Christ, began, in earnest, and this included offering Salvation to the world.
Jesus came to the JEWS... = The House of Israel.
Paul came to the rest.
Understand?
The WORLD is mostly Gentiles, so, Jesus chose ONE MAN, to be the "world Apostle"... = Paul, the "apostle to the Gentiles".
If you study His ministry..
He wrote all the Church Doctrine,
He built most of the NT Churches that are listed as His "Epistle" titles.
I teach that he wrote Hebrews, and i can prove it, but, thats not this Thread.
Even PETER... said... that He had Paul's Letters, and that Paul's letters were """"SCRIPTURE"""... before they were in a NT hundreds of years later.
So, that is PETER, saying that Paul's LETTERS, were equal to the TORAH... Equal to the OLD TESTAMENT.
He was right.