Hi
In response to your post, you need to clarify the below mentioned points in order to have clarity and give you proper guidance on the issue:
A. Whether the said POA registered ?
B. What is the nature of said POA ?
C. Whether the Principal authorized POA to transact the sale and receive sale consideration on behalf of Principal ?
D. Whether your sale deed capture the total payments made by you ?
E. Confirm whether he (actual owner) is aware of your sale transaction, if yes, with material proof.
F. Finally the POA needs to be perused to have clarity.
In response to your query, assuming that the above points are in your favour they are responded hereunder:
Reply to your Q.No.1:
No, he cannot, subject to aforesaid points going in your favour.
Reply to your Q.No.2:
No, he cannot. He has to prove that your transaction is wrong / forged etc., which under the given situation may not be possible for him.
Reply to your Q.No.3:
Yes, you can. Firstly, be doubly sure that your sale transaction is valid, correct and as per the relevant provisions of law. Thereafter, issue notice to him and also lodge police complaint against him.
Best Regards !