What is a minimum age when child can sleep in separate bedroom? Is their any law /age limit when parent can sleep child in separte bedroom?

Birth.

Yes, at birth the hospital takes them to a different room, most parents have a separate bedroom for child shortly after birth.

I don't understand your question. I've never heard of any laws that say anyone or any group of people have to live in a dwelling with any particular number of bedrooms, or any for that matter.

Why do you ask the question?