Delay by Builder

We bought an under-construction apartment in 2006 in Mulund Mumbai. At the time the builder had promised to hand the apartment by mid 2008. The apartment was apparently being built in an area deemed to be forest land. Around 2007 all builders were asked to stop construction by the court until further notice. The matter was finally resolved when the supreme court ruled in favour of the builders and declared the land not to be forest land in early 2015. Clearance for resumption of construction was given. Now when we approach the builder to give us an estimated time of completion, he is not giving any firm commitments and hinting on applying escalations (he has not communicated anything formally but is verbally indicating that there may be cost escalations). He has also indicated that he wants to raise the number of floors and requires further clearances. These are deviations from the original plans. Further, he claims that there are new building regulations being enforced and they may have to resize the apartments to fit the new building regulations. The builders marketing department is heavily advertising the additional floors all over the media/net. Where do I stand in such a situation? 1. How do I get the builder to formally communicate his intentions? 2. Is he allowed to deviate from the original plans without the consent of all the current owners. 3. How can I get him to commit to a completion time and formal handover? 4. Is he allowed to ask for cost escalations when the apartment was fully paid at the time of purchase and registered in my name. 5. Can the builder be served a notice from a lawyer (without necessarily registering a case) which would force him to respond within a timeframe? 6. Can any form of case be registered against the builder at this stage? Thanks for your assistance and guidance.