Stamp paper or register

You are wasting your time.  You should get in touch with a local lawyer who is well versed in properlty law, show the papers that you have, discuss the matter and take immediate legal action, without further losing time.

But never give physical possession,--this is more important.  Contact local reliable advocate for precise remedy and preserve all such payments made to him.   Unless the deed and conditions for such sale or studied, any guidance given may not be proper.