Father property

Hi, MY Father had a property bought 40 years back it is PORAMBOKE" land in chennai. He transferred the property to my mother to get 2 cents patta which government gave for free. To get loan again my mother registered this 2 cents land to my fathers name again. Now 2 years back we gave that house for rent and the rented person is aware of it and he was interested to buy the land. He payed the initial amount for the land with the house and he told within one year he will complete all the transactions. After 1 year he told, he was not able to register and he will pay small amount again as advance and created a agreement that he will pay in 2 months remaining, as he told he is trying to register it. It is almost 2 years still he is not completing it and he is saying waiting to get registration. As we all know that we cannot register, but still he has belief that it can be registered. Kindly let me know whether registration can be done for this 2 cents to them and given or is there any way we can transfer this property to them or registration can be done for it. Need help for it. Thanks, R.Girish