Buying dda property

Dear Sir, I have searched a DDA MIG flat at Dwarka, New Delhi and wants a home loan to purchase it. Now I have a query about legal valuation of the property papers. The property details is as below:- The property is alloted by DDA in Feb 1997 to a person "A" on free hold basis. Thereafter person A has done GPA, SPA (registered) in the name of B in September 1997. An agreement to sell & purchase (unregistered) and will (registered) in the name of B's Wife is done on the same date by A. On the basis of SPA/GPA as a attorney of "A" , B makes conveyance deed on behalf of "A" (original allotee)on the name of A on Feb 2000. Thereafter "B" on the basis of SPA/GPA as a attorney of A, makes a sale deed in the name of "C" duly registered on April 2001. Now I want to purchase the above property from person "C" who is in the possession of its all the original papers till date and claiming his ownership on the basis of registered sale deed on April 2001. Sir here my doubt is " As the GPA/SPA has been done in the name of "B"(registered) and agreement to sell & purchase (unregistered) and will(registered) is made in the name of B's Wife the sale deed (registered) done in favour of C by B on the basis of attorney of "A" is legally valid ? whether the title of the above property is clear in the name of person "C" Whether the will will be treated null and void after the conveyance deed done in the name of original allotee on Ist February 2001 Kindly clear my doubts. Thanks in advance. A.K.Sajwan