Dear Anurag,
Thank you for your query! I am Aadil and I will try to answer your question.
The short answer to your question would be NO, you do not have to take any extra step before you go ahead with their sale.
According to the Apartment Ownership Act, 1989, the buyer of an apartment or flat has complete ownership rights over the said property. They have the right to demand all legal documents concerning the property from the seller/developer, the right to decide who may enter their property, the right to enjoy their property provided they do not infringe the rights of others in the process, the right to rent out their property and expel their tenants upon default, and also the right to sell their property.
It must also be noted that the owner of the property also thus owns a part of the land upon which the said property stands, that is the right to own an undivided share of land (UDS).
Thus the owner of the property does not have to worry about any extra legal procedures before selling their flat/apartment.
I hope this helps. Thank you for your time and patience!
Regards,
Aadil