You did not discuss lack of imputation in your first post. Infants go to paradise immediately upon death-even the infant born of pagans. Of course no sin is imputed to them. The age at which imputation of sin occurs is left to God’s judgement. I think God will respect human good faith judgement on the issue. “Suffer the little children to come unto me.”
I know that many lifelong Christans have claimed to have committed themselves to the Lord at an early age, and even been baptized then; but I personally think it would be wiser for them to wait for the water baptism into discipleship until the point that they are rather freer of the motive to do things based on pleasing mommy and/or daddy, and are coming through the hormone hothouse transformation and into a responsible young adulthood where the decision is more likely both intellectually and heartwise secure.
In fact, I have seen others for which this early promise was not borne out into their adult life. So we ought to be very careful with this. Baptizing children is a pretty tricky proposition. It's not one in which we can blindfold God as to the reality of the child's spiritual state, and how He is going to deal with it. Infant baptism is a very foolish procedure, and has nothing to do with heaven or hell for the child.
But in fact, the doctrine of salvation and spiritual birth is attached to a saving irreversible faith, and not at all to the subsequent rite of public announcement of one's commitment to Christ, which is all and only that which the water baptism connotes.