Composition dealer eligibility

I own a shop having average annual turn over (between 20 to 75 lakhs) .I do interstate purchase and from unregistered dealers in u/s 6(2).  (1)Can I opt for composition scheme? (2)Can I do purchase from out side state and from unregistered dealers in composition scheme ?  (3)Should I take closing stock details of 30th June in any aspect. (4)Is there any liability to pay tax for the stock in hand on June 30th ?