You have two option one is claim of advance money with interest another is claim of early possession,so you can send a Legal Notice to the Builder/Promoter as per your wish.If the builder would not comply as per Notice then you can file a case in District Consumer Forum or State consumer Commission as the case may be for deficiency of service and damages for delayed possession.

Products and services by builder are covered under the Consumer Protection Act.

If you have grievance against builder, send a notice to him in writing. Do not worry if he refuses to accept your notice as only proof of sending is required. Send the notice by registered post or Under Postal certificate. Retain the proof of sending.

you have not mention the period mentioned by the builder when possession is going to be handed over by the builder?

if as per agreement possession is going to be handed in mid 2015 or latest by diwali 2015 wait for possession to be handed over . moving consumer for refund of money is not a good idea as you lose out on capital appreciation in flat values in bombay .

even if you file a case in consumer forum it would take 2 years to be disposed of . best bet is to wait for possession . if there is delay in handing over possession by the builder then under the agreement builder would pay you interest for delay in handing over possession

send a Legal Notice to the Builder/Promoter as per your wish.If the builder would not comply as per Notice then you can file a case in District Consumer Forum or State consumer Commission as the case may be for deficiency of service and damages for delayed possession.