To the original question, we've been born again when we place our faith in Jesus Christ for our salvation and confess him Lord of our lives. What does born again imply? We have been created anew, a spiritual creation, born again by God's will, not the will of men (John 1:12-13). We've been born again into God's family, adopted by the Father. I always tend to think as simply as possible, since the Gospel can be taught to a child. We've been shown grace and mercy. Now about the issue such as the adulterous woman caught in the very act, Jesus shows compassion, and she believed on Jesus. She was born again. He told her not to sin again. Going to 1 John 2:1, "My little children, I am writing these things that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous; and He Himself is the propitiation for our sins".
Like most of us, if we were her, we would bring baggage along in the flesh to the newly created spiritual man. Jesus knows we will sin from giving into temptation because of this baggage, and Romans 7:14-25. The proof is 1 John 1:8, "If we say that we have no sin, we are deceiving ourselves and the truth is not in us." So what about 1 John3:8, where it says "the one who practices sin is of the devil;?" Unbelievers practice sin. Believers can fall into sin, but don't glory in their sinfulness, and therefore don't practice it.