first I would like to clear is, in the absence of any valid sale deed, you cannot claim the ownership of the property, and transfer of property have not taken place for the past so many years, as there was no sale deed done, the ownership remains with the same person, who had made offer to sell that flat. In the absence of the above said document ,you cannot enter into any sale agreement as seller. Only on execution of sale deed, you become absolute owner of the property and transfer of property will take place. All other things, pertaining to effect the sale deed will not demonstrate or give an impression as you are the owner of the said flat. It is only a myth. Forget all other things and do the sale deed as soon as possible.