1) you should never book flat at pre launch stage
2) only after building plans are sanctioned and CC issued should you do the booking of flat
3) avail of bank loan so that bank does due diligence of the project
4) if builder is willing cancel your booking and take refund .
5) it is better to pay higher price only after approvals are in place than making payment now . you should take a gamble with your hard earned money
6)in the alternative check the track record of builder whether he has completed other projects on time . then take call for making further payment
7) you would be eligible to file complaint with RERA in case builder has obtained the approvals for launching the project