Buying a propery

Hi Sir, I am planning to buy a flat and requested owner to share the property document. He shared following document. First Document Certified copy of the agreement of Sale from Builder to Mr. XXXXX in 1988. This is registered agreement and stamp duty is paid. No loan taken by the buyer. Second Document Mr. XXXXX sold this property to Mr. YYYYYYY in year 1995. An Agreement was done on 20 Rs stamp paper. Stamp duty is also paid but not registered. Mr. YYYYYYY has taken a loan to purchase this properly from BBBBB bank and Bank has collected certified copy of first agreement, and second agreement on 20 RS stamp paper. Bank closed the loan account and return the same document to Mr. YYYYYY. At present the property is in custody of Mr. YYYYYYY and he rented out the flat. Now when I plan to buy this property, my bank mentioned that, Bank required original copy of the First agreement and original copy of the second agreement and both agreement should be registered. Now I have following queries 1. Should I buy this property? 2. Is there any way, that second agreement from Mr. XXXXXX to Mr. YYYYYYYY. 3. Does it mandatory that both deeds should be registered 4. Mr. XXXXXXXX is not available (died) then H