That Jesus is saying it is only by doing what I tell you that you can be saved and what I tell you is eternal, not just beginning with me.
I believe that the reason for the appearance of Jesus was to get man back on track, that believers had strayed and become ends unto themselves, especially those who represented the church.
...then those whom God intended for Eternal life..., are raised to Eternal life the same way as New Testament saints, by God's grace alone, through faith alone, in Christ alone.
That still leaves hanging the pre and post Christ periods but, more importantly, it suggests that the anointed ones are pre chosen and either you are or you are not. If so, it matters not what one does, he either is or isn't. I don't believe that.
I do believe it is by grace that we are saved but not that it is preordained. We need to consciously and diligently seek it and because God knows our hearts he knows whether we are sincere seekers or not. If we are, He grants our entry through his grace.
That is in comparison, according to the scriptures, of those who act out belief and try to earn their way into Heaven through good works.
This is consistent with his attack on the money changers and his admonition to go into your closet to pray rather than making great public displays of your actions.