Note that there is no registration receipt and also NO POSSESSION letter from builder. Seller is saying that since society NOC is there, we don't need vacant possession letter from builder to him. Is it true?
It is not so.
The seller may give some lame excuses which are not valid in the eyes of law.
You have stated that the vendor is having sale agreement, but sale agreement deed is different to that of the registered sale deed, did you get that?, if not then ask for the original sale deed standing in the name of the vendor who is selling you the property. NOC from society is also a different subject.
Index-2 was created recently as a True copy (original was not there). In this true copy they have defined the flat number, names of the parties and market value. They have not written PAN numbers and stamp duty value.
If you suspect the genuineness of Index-2, then you may have a second thought to buy this property.
There is no registered sale deed. At the maximum owner is willing to create FIR, newspaper notice and bank indemnity for lost registration receipt. Lawyer report says that flat has no encumbrance and has clear title subject to condition that builder's vacant possession letter,, registration receipt is available.
Why there is no registered sale deed in favor of the vendor who is selling the property to you?
Without a registered sale deed executed in his favor, how does the vendor claims title to the property?
Or how do the lawyer certifies that the vendor is having a title to the property?
Without marketable title to the property the vendor cannot sell this property to you, so probe into the details before deciding to buy.