or, to choose to do evil instead of good, BEGIN AND END?
The condition known as Original Sin, is a doctrine attributed to
Saint Augustine.
While the Bible tells us by one man, Adam, sin entered the world.
Whereas we are told we are each responsible for our own sins. Sin of course being, "an immoral act considered to be a transgression against divine law. "
Ezekiel 18:20
20. "The soul who sins shall die. The son shall not suffer for the iniquity of the father, nor the father suffer for the iniquity of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself." The Book of Ezekiel chapter 18
To answer your question, at whatever age a child matures enough to know right from wrong is , I believe, when that same child can choose to do evil, or good. Newborns are sinless, as we know. No one is born damned.
17. "So whoever knows the right thing to do and fails to do it, for him it is sin." The Book of James chapter 4
3. And said, “Truly, I say to you, unless you turn and become like children, you will never enter the kingdom of heaven." The Book of Matthew chapter 18
14.But Jesus said, “Let the little children come to me and do not hinder them, for to such belongs the kingdom of heaven.” The Book of Matthew chapter 19