Yes the booking form forms part of the SPA. There is a binding contract between the buyer and the agent. Offer, acceptance, consideration ITCLR. Refer contract act 1950. The fact that you purchased the unit was due to the offer promised by the agent. Hence the law will not allow unscrupulous agent to renege on their promises. What u need to do was Just sue the agent and his/her agency. You do not need to include developer in Your suit. The agency will Make the developer as a Third party If indeed there was binding agreement between them on the offer being promised. A Classic Common straightforward case in court