Hi,
Have you executed Unit/Apartment Bueyr's Agreement?
If yes, kindly contact a local lawyer of Gurgaon and issue a notice. Though, I am sure agreement is executed.
However, as per construction updates on the said project, there are some constructions which are shown. So I am not sure, how you are saying construction has not started.
Have you taken any home loan towards the same? If yes, stop making the due payment when the builder demands.
Or, best way contact the head (Not Sales and Marketting team) and request for cancellation and take back money. They might go for forfeiture so in that case they do not have right to do so as fault is from there side or ask the builder to shift to any other project of them and transfer the paid money, accordingly.
Personally, 4 year by Vatika is not big and you have to atleast wait for 2 years but if construction has not started, you may contact the boss direct, either cancel or transfer or issue a notice
All the best