A. Let’s look at what we know and start with this question, “can there be sin in heaven?” The answer would be yes. We know that Satan was created perfect. He was an anointed cherub until he rebelled (sinned) against God and was cast out of heaven (Ezekiel 28:11-19). When this happened, he took a third of the angels with him. So there were many angelic beings who exercised their free will and sinned against God.
So the Bible tells us that there has been sin committed in heaven. Often people will say that God cannot be in the presence of sin, but that is not biblically supported as indicated by the rebellion of the angelic beings. What we do read is that God is just and holy, and did not allow sin to remain in HIs presence. God judged the angels and imposed the penalty of separation from His presence.
Q2. If angels have free will to choose to obey God, does man [have this choice] in heaven?
A. When one repents and trusts in Christ’s work on the cross to pay for their sins, they are freed from the penalty of sin and, during their earthly life, they are being freed from the power of sin by the presence and power of the Holy Spirit. When we leave these earthly bodies and go to be with the Lord (2 Cor 5:8) we will then be freed from the presence of sin.
So the underlying question may be, should we fear a second fall?
That’s a good question because, IF (that’s a hypothetical “if”) man were able to sin in heaven, then God would have to judge that sin and cast the person out from His presence, just as He did with the angels that sinned.
We know that will not happen because our new life in Christ is eternal life. Christ’s death on the cross paid the penalty for our sin and it was sufficient to both save us and keep us. We are His and we will be with Him forever. Nothing can separate us from Him (Romans 8:35-39). He will never leave us or forsake us (Heb 13:5).
So your question about whether man has free will in heaven is not answered in Scripture. There isn’t any Scripture to conclude that our free will is going to be taken away. However, what is clear is that we will not sin because we are secure in our salvation, due entirely to the righteousness of Jesus Christ, which was imputed (credited to us) the moment we were saved.
So, our boasting throughout eternity will only be praise to God for the righteousness of Christ than seals our souls eternally, from the penalty, power and presence of sin!