You have not been vigilent. Probably you stand duped.
You cannot say that you have purchased a land on Rs. 100 stamp paper. You cannot claim clear title of the property unless you have got a Registered Sale Deed in your name.
It is not clear why you waited 6 years for getting the Registration done?
It is not clear what the terms in the agreement are. Without knowing the terms, it will not be possible for any one to give any views.