Will Christians in heaven be able to reject Christ? Or will their freewill to reject Christ be taken away?
Will those in the lake of fire have freewill to accept Christ? Or will their freewill be taken away?
This seems off topic but I will address them:
First off: Every knee will bow and “acknowledge” the existence of Christ as Deity, but that will not “save” those that go to hell. For those that go to hell accepting God charity would be like putting a gun to the person’s head and saying Love me or else. A forced Love is not a Godly type Love. They had their opportunity on earth to make a truly free will choice to accept or reject God’s charity and they refused, so that choice has been taken away from them. They will realize what they did and blame only themselves.
In Heaven you still have free will (like the angels, some of whom rebelled against God).
When you say: “Reject Christ”, what are you talking about, Christ is in your presence helping you in the form of the Spirit which you now can see and tough 24/7?
The tree of knowledge or something similar is not there to tempt you, satan is no longer around and you have experience with both sin and satan, so there is no temptation to learn about evil.
Lots of temptations can go back to the conflicts sexuality creates, yet that goes away by no longer being a sexual being.
God has given us everything, so what is there to covet?
To be like God comes with having Godly type Love (unselfish) like God, so do you desire to be even more unselfish (OK, but is that something to covet?)
Sin is needed on earth to help humans initially fulfill their earthly objective, so God does not arrange earth to be a place to avoid sinning, but sin is not needed in heaven, so everything is there to help you avoid sinning.