BELIEVERS born in the Kingdom Age, after the 1000 year reign of Christ; What happens to them?

That is a good question isn’t it?
The Bride of Christ (believers living today in this dispensation of the age of grace) received immortal resurrected glorified bodies at the Rapture, The Old Testament saints were already resurrected at Christ’s Second Coming event. Surviving believers from the Tribulation period enter the Kingdom age to repopulate the Earth.  But what about those BORN in the 1000 year reign of Christ on Earth, before the Great White Throne judgement of unbelievers?
We know by Scripture that US living TODAY in this age of grace dispensation will not be judged at the Great White Throne. Only the DEAD who rejected Christ.
We will ALREADY be bodily resurrected and in the New Jerusalem – that heavenly city.
But Salvation in NOT BY WORKS. And those being judged to the lake of fire at the Great White Throne Judgement are the unbelieving dead who now reside in Hades.  In Hades, only the torments side has the unsaved dead in it. The paradise side is empty – Jesus took them to Heaven just after the cross. They are judged by their WORKS – not faith. Believers are saved by FAITH – NOT WORKS.
One possibility is where in Rev. 20:15 says, And whosoever was not found written in the book of life was cast into the lake of fire.
It might seems interesting that John mentioned the Book of Life. If this is a judgement only for the unsaved dead, why mentioned the Book Of Life?  Some may conclude that  believers who die during the Millennium, will be found in the Book of Life and will be resurrected. It does seem plausible, but I am conflicted on this because at the Great White Throne, the judgement is based on works and not faith alone in Christ. Because of this I do not think that is a correct assumption. Why would the Book Of Life be checked to see if they are in the Book of the saved then? Well, this is court of God. In a human court, do we not need to present the evidence of why someone is to be convicted? First and foremost, the need to show the person that they did not get born again is evidenced by the Book of Life. Once that is shown as THE MAIN EVIDENCE (because salvation is only by faith – not works, and it shows them how they rejected salvation through Christ), then they are judged by their works. This makes more sense to me.
Also, in Rev 20:5, we see that the subject is about the 1st resurrection, describing the Tribulation saints. ‘Blessed’ are this group of believers. The ‘rest of the dead’ are those dying in the Millennial reign of Christ. Rev 20:6 The second death has no power over the believers. Possibly, according to Rev 20:5 the millennial believers are resurrected at the end of the Millennial reign.
This question is one many ponder. Although we are not given the answer specifically, I see no other option in my limited knowledge.  Yet, either way, I trust God will do right for His believers in the Millennium reign of Christ on Earth.