Dear Nilesh
Formation of society is for governance and maintenance of the apartments which is not the part of execution of sale-deed. Society can be registered at later point of time when all the flats/ apartments are occupied by the residents of the scheme. Ask your builder to execute deed of Apartment & Deed of Conveyance in your favour, you having paid the entire amount of consideration towards purchase of flat.
That, in the event, the buiolder fails to execute deed of Aaprtment & Deed of Conveyance in your favour, issue a legal notice duly served upon him and file a complaint u/s 12 of Consumer Protection Act for deficiency in services on the part of builder and pray the Consumer Forum for directions to the builder to execute Deed of aaprtment & Conveyance deed in your favour along with compensation for mental agony.
Feel free to communicate in case you need more advice.