Job was not Jєωιѕн.
You are technically correct, but for purposes of this discussion, Job was a follower of God's law.
Job lived in the times AFTER the Garden of Eden, but before Moses. Many say that Job was a relative of Abraham. But the term "Israelites" didn't even exist when Job was alive.
There were basically 2 camps of religious people in those days....those who worshipped the True God and those who didn't. So, you are correct, Job wasn’t “Jєωιѕн” (nobody was, in his time) but he was a worshiper of the same God, Jehovah, as was Abraham.
For purposes of this discussion, would Job have believed in the coming Redeemer? If he believed in Jehovah and followed the 10 Commandments, then yes. Ergo, belief in the Redeemer made him "pre-Jєωιѕн" or "pre-Israelite"....i.e. he followed the true religion (at the time he lived).
Plato lived much later in time, when the Israelite religion was mature and known by the Greeks. Plato was not Jєωιѕн, nor an Israelite. Plato did not worship the True God.