Did Peter understand God's move from Israel to the Gentiles?
No. Peter for the most part had no comprehension of God's move away from Israel and the covenant promises to the Gentiles with the gospel of grace. Later, Peter wrote that Paul's writings were things hard to be understood, confirming his struggle.
Les teaches that Peter, for the most part, had no comprehension of God's great move to come away from Israel and the covenant promises and go out to the whole wide world, Jew or Gentile, with the gospel of grace. Les explains that this truth was unknown until Paul, and he disagrees with those who say there is no difference between Peter's message and Paul's, calling the difference daylight and dark. Les notes that later in Galatians 2 there was a difference of opinion, and Peter himself wrote in his second epistle that Paul's writings are hard to be understood.