Power Of Attorney

I will start with an apology as I may go overboard trying to explain the situation. 1. The owner initially took an amount X for the property. 2. He even did a sale deed towards the advance 3. We found the property has a mortgage in a nationalized bank 4. The deal did not move for a while. 5. In the year 2012 when the bank attached the property the seller pleaded with us and we paid again an amount X to the bank. 6. The bank did not close the housing loan rather disburse the fund across different loan accounts (Like CC, Personal and Housing) 7. We never got the NoC from the bank and were not able to complete the registration process 8. The seller executed a PoA on my brother's name with a promise that he will get us the NoC from the bank. 9. It's now little more than 4 years and we are afraid he may sell the property again and seems have taken advance from another potential buyer. Please advise -. 1. Can he execute the sale deed? 2. Can we still take possession of the property even if the buyer executes the sale deed? 3. Can we move to a court and request for a Gazetted notification?