Validity of unregistered agreement of sale on a 100rs note

It does not have any value if not even Notarised.

It has been signed by both, the seller and the buyer as well as two witnesses.

All the agreements which are whether registered or not have to be proved for the intention of execution in the court and specially if these are pertaining to the immovable property these has to be registered otherwise it will not be enforcable by law. As in that position first the intention and the validity of the executors is to be established in the court.