Query on Purchasing a Resale Flat

I am looking to buy a property in Mumbai Suburbs. The property that I have selected is a resale flat (constructed in 1982). Originally the flat was bought by Mr. Tulsiram Sharma (in 1980) from the builder/developer for Rs. 70000/- to be paid in 6 installments. However, before paying the last installment Mr. Tulsiram Sharma sold it to Mr. Sumit Agrawal & Mrs. Shweta Agrawal (in 1982) for Rs. 96000/-. Then in 2010,Mr. and Mrs. Agrawal gifted the flat to their daughther Mrs. Geeta Jhunjhunwala (I.e. after daughter's marriage). For the said flat the seller has given me the following documents: 1. Chain of Agreement 2. Share Certificate 3. Society Registration Certificate 4. Occupation Certificate 5. NOC from society 6. Latest property tax receipt 7. Approved Layout Plan The consideration for the same will be paid by taking loan(45%) and own contribution (55%). My queries are: 1. First 2 agreements are neither registered nor notorized.(I.e agreements between builder - Tulsiram & Tulsiram - Mr. And Mrs. AGARWAL). Since these are unregistered what action can be taken now to correct this defect. However the gift deed ( the last agreement) between Mr. & Mrs. Agarwal - Geeta Jhunjhunwala is registered one. 2. Since the flat that I will be buying is a gifted one, do I need to take any NOC from family members. 3. The Conveyance deed of the property is still in the name of the developer/ builder. Should I purchase such property. 4. Do I need to verify any additional documents apart from the above mentioned 6 documemts. 5. Since I will be taking a loan, where bank will also be doing the necessary legal and technical verification, should I get the title search for last 30 years independently. 6. Does Maharashtra has facility of online stamp duty, registration fees payment, registration of sale agreement, etc. 7. The flat will be bought under co-ownership. So should we mention the %age of ownership in the agreement.