Buying a resale flat

When the flat is already transferred in the names of X & Y, which agreement is referred to have been lost ? 

Whether the agreement (stated to have been lost and duplicate copy obtained) was registered ?

What is the relevance of the agreement at the time of sale of the flat to prospective buyer ?

Get the title report searched properly, however, if it is "FREE FROM ANY ENCUMBRANCE" get a second opinion as the same (title) is under suspicion.

Whether gift deed by X to his wife is registered or not ? If gift derd by X to his wife Y is not registered then Y is not absolute owner and can only sell her share.

Agreement from builder to owner is lost , later they filed FIR and then got the certified copy . I consulted with lawyer he did the search title report for me .lawyer said it's clear no problem ..later Bank also did the search title and they said it's clear..

It will be in your interest to take the consent signature of Husband to the sale.