re: “God’s question to you will not mention sin at all (they don’t exist anymore) but will be: what did you do with what my son did for you on that cross. Any one who does not understand this, does not know Bible doctrine.”
Many Christians get confused on this idea. The idea is that the only sin people will go to hell for is the sin of rejecting Christ.
Yes and no. We are already dead in our sins for the sin in our lives that we’ve committed against God prior to accepting or rejecting Christ. This is a deep subject, but carefully read Romans 5. Basically the teaching is:
1) Sin and death entered the world through Adam and his
sin.
2) All of us sin and break God’s moral law, we are
therefore all sinners, helpless to remove the guilt of
our sin ourselves - we are already in a state of
condemnation before hearing anything about Christ.
3) If God had never sent Christ to take the punishment
for our sins, we would still justly face that
condemnation without hope.
4) God was/is under no moral obligation to do what He did
for us in Christ Jesus because we have all broken His
law.
5) On the other hand, if we reject the salvation God
offers us, the salvation He provided for us in Christ
Jesus - then we have no hope of salvation because that
was it - there is no other lifeboat.
So, yes, rejection of Christ seals our condemnation, but we stood condemned already because of our previous sins against God. But, it is also not exactly true to say that the ONE thing that sends us to hell is the sin of rejecting what God’s Son did for us on the cross. If God had never sent His Son, we would still be condemned to hell by our sins against God’s moral law.