NOC for property on my Father's name

Dear Sirs, My father owned a Tamilnadu Housing Board property in Vellore purchased by him in 1985. He died in 2016. Sadly, my mother also had passed away a year before him. The flat was registered in my father's name and thereafter we have obtained the legal heir certificate for this property and other various liabilities under both myself and my younger sister who is married and also resides in Chennai. A mutual understanding between myself and my sister to sell this property has been decided whereas I do believe she would have to provide me with an NIC in order to handle the sale process and other formalities when negotiating or finalizing discussions with prospective buyers. is in the process of selling this property. I would also like to know if the property NOC has to be separate from other NOCs that needs to include the other liabilities mentioned under the legal heir certificate (car, gas cylinders, telephones, taxes, bank accounts etc). Do we have to provide such a NOC to the buyer? If so, I would appreciate your help to please provide a format? Thank you.