Gst queries

1) A recipient is under composition scheme. He is purchasing product from unregistered supplier or a supplier who is also under composition scheme. Whether the recipient has to pay tax under RCM? 2)Suppliers who are under composition scheme has to submit the return quarterly, 18th of following month. The supplier might have received supplies with tax. The supplies received will be auto populated by GSTR1 . Whether the supplier has to verify the GSTR2 every month in this case? If yes if the supplier is also under composition scheme he will submit the return only quarterly and on 18th. Then how to verify it? 3) What is black credit. Why the supplies/services mentioned under this, coming under black credit? 4)Recipient who is under exemption for his supplies purchasing product with tax. Is there any provision to take ITC and get back that amount? There is no MRP here after. If I am buying a paste what will be the rate printed on the package?