The Greek of John 1:1 is such that when the beginning began, the Word was already in existence. And as I previously stated, “firstborn” does not necessarily mean one that came into existence, one who is literally firstborn. It can mean that one has the rights as of one who is the firtsborn even though they actually aren’t the firstborn. That is a legitimate biblical usage.
In regards to Jesus then, it means that he is preeminent, he is Lord over all creation. It does not mean that there was a time when the Son did not exist.
Just as “one God, the Father, from whom all things came,” speaks to his eternal existence, so “one Lord, Jesus Christ, through whom all things came,” speaks to his eternal existence.
It is exactly the same language. And if Paul is right that “all things came” through Jesus, then logic tells us that Jesus cannot be one of those created things. This is in perfect agreement with John 1:3 and Col. 1:16-17.