Index 2, legal heirship

"Now the society is planning to register the conveyance deed" how and under what authority. It appears that you are misinformed.

Hi sir,

There was no conveyance deed made earlier between the developer and the society, the building is around 40 years old, so they are planning for redevelopment, for that they are executing a conveyance deed now,

My question is that whether a heirship certificate is required if the owner has passed away for his legal heirs to put their name on index 2

Yes, it is essential that you obtain a legal heirship certificate from the revenue authorities and get the revenue records transferred to the names of the legal heirs from that of the owner after which you can give the copy of the transferred records to the society so that they can record the new owners name for conveyance and redevelopment etc.