Power of Attorney

Mr Rajan was living in Mayur Vihar, Delhi. He purchased a plot in a city in Tamil Nadu. He borrowed money from his friend Ganesh in Delhi. Since Rajan cannot repay the loan, he willingly gave the plot to Ganesh in lieu of that loan. Instead of making sale deed, Rajan gave Ganesh power of attorney (POA) for that plot, because Ganesh thought he could give back the plot to Rajan if he repays the loan. This happened in 2010. But Rajan died in Delhi in 2012. In 2013 POA rules have been changed and so, I think, that POA is invalid now. Original land document (registered sale deed) written in Tamil is with Ganesh. Rajan had two sons, both liviing in Delhi. (Both of them knew this deal) Ganesh wants to sell the plot because he needs money. What are the options before Ganesh to sell the plot? What documents are required for that? According to my knowledge, these are the options: 1. Rajan's sons go to Tamil Nadu with legal heir certificate and their original IDs and sign the sale deed on behalf of their father (and give the money to Ganesh). 2. Rajan's sons give POA to Ganesh in Delhi, then Ganesh goes to Tamil Nadu and sell it. In case of the second option, is it legally possible to write and register POA in Delhi for a plot in Tamil Nadu (plot sale deed is in Tamil) ? If so, in which registrar office it should be registered? What are the documents required for that POA? Is it possible to write POA by any one of the legal heirs, because one son is always out of Delhi? Kindly advice the procedure. Thanks in advance