That doesn't answer the question did you read it?
If there's no sin in the 1000 years then what about child who rebels will be instantly killed and placed in Death?
You just contradicted yourself
A dead human is no longer on the earth. A dead human is a dead sinner. Not a living sinner and sin does not enter the world.
Adam kept living in a dead condition called sin. The instant a child disobeys they are dead. Not like Adam's sinful corruptible dead flesh. A person who disobeys is no longer enjoying life, but dead dead. There is no recovering from that state.
Do you not understand that when Adam disobeyed, he let sin into the world? That will not happen in the Millennium. You only disobey one time and you are gone.
We disobey and sin, because sin is in the world. Adam did not have a sin nature nor was there sin in the world. The first time Adam disobeyed, not the umpteenth time, Adam literally physically died and literally spiritually died. That was it for Adam, he was dead. And now living in death, a functioning mortal (death).
The condition we are in now, is not the human condition in the Millennium. One chance and you are gone. If there was sin and a sin nature all would be gone, and the earth empty. So disobedience is not a contradiction, because disobedience is simply breaking the law. Not breaking the law while in Adam's dead corruptible flesh. The point now is no one can even obey the law. It is impossible.
Breaking the law in the Millennium will be impossible. However if you do, it will only happen once and then you end up in the LOF when Death is emptied out. But Death is not living on earth as we do in Adam's dead flesh. Death is where one goes instead of going to sheol today.
Before Adam there was no disobedience, because there was no law, and no sin. Now we cannot keep any law, because our sinful nature constantly condemns us to a state of death. In the Millennium there will be laws, but no sin, because people will naturally obey all the laws and suffer no consequences.
The ability to disobey is not a contradiction. It is considered a curse, and that individual is removed from society. Sin does not enter, and people don't live in a dead state of a sinful nature.
Paul does not call Adam's disobedience sin:
"Nevertheless death reigned from Adam to Moses,
even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come."
I call what Adam did disobedience, not sin, because sin is not a thing. Sin was not in the world. Adam could not have sinned, until he died, and in a state of death. Adam is a type of Christ. Christ obeyed God in all things in His human form, thus a sinless Lamb. Adam disobeyed and broke type, so he lived on in a state of sin, that he passed on to all of us. All those in Christ receive the state of no sin.
But at the Second Coming there is the complete restoration as a son of God.
So Adam did not sin until after sin entered, and after death reigned. Adam disobeyed. That is why Paul said all sinners are not the same as Adam's transgression. Only Adam could disobey God. Eve could not disobey God, because it was Adam's choice to disobey God. You can argue semantics and claim they were the same flesh, but Paul did not. Eve was the one deceived, not Adam.
So once again in the Millennium it will be like it was before Adam disobeyed. But no one will bring sin into the world like Adam did. All they can do is remove themselves from life itself. That is why it is called Death, and not just a place of punishment. Death is the place where those wait who have been removed from the Lamb's book of life. There is no life or getting a second resurrection out of that spiritual death. The death of rejecting the Atonement, and marked for doing so.
Even those born in the Millennium were still all written in the Lamb's book of life before creation and still part of the Atonement Covenant. They are not born into Adam's dead corruptible flesh. But disobedience is still a thing with laws still being a thing, but not the OT Covenant from Sinai. This is that new covenant promised after the 70th week is over. And not the NT Covenant based on Adam's dead state. It is the Covenant of the iron rod, except all are naturally born into obedience. Only, according to Isaiah one can still disobey, but immediately removed, and it will not happen to those past 100 years of age. Which once again, at the end, the largest demographic on earth will be those under 100 years of age born in the last 100 years. The one's who will listen to Satan and an easier target. Just like Eve who was the vulnerable target to get to Adam.