"What difference would it make if he was one year old or hundred years old when God created him? He was created by God as a “FULLY GROWN MAN” and not as a child."
Big difference. The word of God says he created a MAN and not a child, or a boy. God also created a Woman. Not a child, or a girl. Which means that THEY WERE OF AGE.
If God created Adam as a 1 day old Babe boy, and LATER CREATED EVE also as a 1 day old Baby girl, then we know for sure that Adam is older than Eve. However what does the Bible tell us? It tells us that He created MAN and (later) WOMAN. NO AGE IS MENTIONED OR EVEN ALUDED TO.
What were BOTH THEIR AGES?
Neither YOU NOR I can EVER TELL this through what is revealed in the Bible.
When a youngster comes to me and asks many of these practices that we follow and strictly adhere to, we need to give answers that ARE SUPPORTED FROM THE SCRIPTURES else we must simply confess the truth - these are practices, customs and are not condemned by scripture hence we continue to practice them as it is our personal preference.
To legalize and say something is sinful when no scripture instructs or even aludes to is a stumbling block to our youth and also make us, stewards of God's word, loose credibility in their eyes.
If two young believers decide to marry with parent's approval, even if the woman is older than the man, there is absolutely nothing that forbids them to marry.
We need to appeal to scripture for all matters.
There are many things that we do every day that Bible has not talked about yet some believers have classified them as sinful.
Eg: For some penticostal groups - taking medicine is sin. Likewise, keeping moustache and beard is sin.
Likewise, for some Kerala brethren, younger bridegroom marrying older bride is considered sin.
What is their basis? Not from the Bible anyway. If anyone can cook up rules like this without scriptural support, why do we need to depend on the Bible for all matters of faith and practice anyway?