But you can claim to be in faith without really being in the faith. That is John’s entire point. God knew from the moment of creation what your and my ultimate fate would be. Why would God save someone he knows he will have to unsave later, maybe back and forth several times? That would be an imperfect God and I don’t believe in an imperfect God.
God doesn’t “unsave” them. They leave the faith. They were in the faith and then elected to leave it. In the early days of the church, many times they returned to Judaism.
In 1 Cor, Paul orders the church to turn a sinner “over to Satan for the destruction of his flesh” so that his spirit might be Saved.
Judas walked with Jesus as a Disciple and still fell. The idea that Jesus chose him in order to see to his ultimate destruction sounds disingenuous.
Free Will means that we can leave or stay.