GPA related query.

With regards to a BDA site, I've a couple of queries to be clarified. Mr. X was allotted a BDA site (Bangalore) in the year 1997 which was entitled to a 10 years lease cum sale agreement. Mr. X has executed a registered GPA at Jayanagar, sub-register during the lease period to the Mrs. Y. In 2000 / 01, BDA passed a circular that the "Lease cum sale" agreement of 10 years has been withdrawn and the Owners can obtain an “Absolute Sale Deed” from the BDA. During this period, Mrs. Y presented the registered GPA to the BDA and obtained the "Absolute Sale Deed". A "No objection" (NOC) was also submitted to the BDA signed by the Mr. X and then an "Absolute Sale Deed" was issued. The "Absolute Sale Deed" from BDA was obtained in the year 2001 by Mrs. Y. In the year 2002, (just a year after BDA issued the "Absolute Sale Deed"), Mrs Y executed a "Sale Deed" in favor of Mr. Z. (Note - Mr. Z is the Husband of Mrs. Y). With this "Sale Deed" in the name of Mr. Z. Mr. Z has obtained • BDA Khata, • Approval for House construction, • BBMP Khata and are paying the Property taxes till date. • Mr. Z and his family are staying at that place since 11 years now. Now, Mr. Z is willing to sell this property. My query is… • The registered GPA was executed in 1997, and the GPA holder has sold that property to her Husband in 2002. Is this considered a valid transaction? • I read in the net that “GPA after sep 2011 are not valid”, since this GPA was executed in 2002 and the present seller has all property documents in his name, can this be considered safe legally and can the property be purchased? Any advise with this regards is greatly appreciated.