Is the following arrangement of rows in the mosque – men, then children, then women – a Prophetic hadith, or was its meaning mentioned in a hadith? What is the ruling on violating it, and what is the ruling on a man pulling a boy out of the row to take his place?

Arranging the rows by having men first, then boys, then women is recommended. Going against this is disliked but does not invalidate the prayer. As for pulling a boy out of the row to put him at the back and take his place, this is an unlawful act because it causes boys to dislike the mosque, creates resentment towards the one who does it, and involves injustice to them. Furthermore, whoever precedes to a place has more right to it.