How many children are we suppose to have before we get the Golden Child?
What is the MAX child we can get?

The birth of the Golden Child is dependent upon specific levels of Village Technology and solving other puzzles, not upon village population (which is limited to 65 villagers on most devices). There is only one Golden Child, and in v1.1 the birth can occur even when you've reached the population limit. If you need more specific help with the puzzles, please see this post.

Thanks. I have finally got my golden child. Do I have to wait till he is 14 to push the boulder away?

The GC never grows older. All you need for the next puzzle is patience!