Cancellation of booking as Builder didn't adhere to his promise

Sir, I booked a flat with a reputed Developer in Gurgaon in the month of October 2014 in pre-launch. At the time of booking the developer promised to launch the project by Deepawali,but they failed to launch. I inquired regarding the same by visiting their office and the developer assured that it will be launched soon as they are waiting for approvals. I waited for another month and still it wasn't launched. Again the same answer by developer that it will be launched soon. Then in the month of December they got the application form signed and I was assured by the developer that they will launch the project by New year without fail that's the reason I agreed to sign the application form. Still the project wasn't launched on New Year and I still waited and the same answer it will be launched soon as some approvals are pending. Then after approximately 3 months they launched the project and sent me the allotment letter but I lost trust on the builder and the project that was to be launched in October was launched after 6 months. Now I requested the Developer to cancel my booking on the ground of false promises but they refused giving reference to the application form duly signed by me as per the clause in application form in case of cancellation I will have to pay 25% of the cost of the flat. I had few meetings with the representatives of the developer and they said the construction of the project will start by end of December 2015. I want my booking amount of 5 lacs back. Note: I have't signed any Buyer's agreement till date so none of the clause in the agreement are legally imposed on me that i need to adhere to. Application form signed by has no legal relevance. Kindly advice!!! Regards Inderveer Vohra