The answer is vague because the question you ask have no clear answer. When the clown change to male, female depends on more than just age or size. The general condition and environment plus size and likely the present of other clowns have input into development and sex of the clown. There are male Ocellaris that is almost 2 inches long while there are also females (dominate of two but not breeding anyway) that are 1 inch long.
The second question regarding the growth rate of clown is also depends of the condition of the tank, and how much you feed them. My A. percula go from 1 inch to 1.25 inch in 4-5 weeks.
Sorry, I don't have a number for you but if I were you, I would not trust a fix number answer for the questions you asked.