If a person A purchases a property for a consideration of say 50 lacs from B by means of sale agreement, GPA and will. A pays 45 lacs at time of possession. but the agreement is unregistered though signed by vendor B and executed by him. it is unilateral…Is such agreement valid???? what if vendor B again sell the property taking advantage of the fact that it is unregistered, to somebody else and this time registers the agreement of sale????