Non-Payment of Interest by the Builder

We had registered for 2 flats with the builder in 2012 for Rs. 34,00,000/- each, & agreed to make payments as & when required by the builder against the promise of the builder to give possession within 2 years, but did not executed any written agreement instead it was all orally agreed. After then we made the first installment on 11th may 2012 to the builder. The total payment made was of Rs. 16,00,000/- for both flats (Rs. 8,00,000/- through A/c Payee Cheque & Rs. 8,00,000/- in cash). Now, its being March 2015, but the possession is still not given & even making delays giving fake reasons, for the repayment of the said amount of Rs. 16,00,000/-. So, my question are: - 1) Is there any time limitation for filing a civil suit for the same?? 2) He has given us with post-dated cheques being dt. till the end of April-2015, so will be able to file a suit for interest thereon, even after receiving our original amount of Rs. 16,00,000/-?? 3) What is the procedure & which sought of suit & where would I be able to file suit?? 4) Also, is there any deficiency in my case or rather will I succeed in my suit?? PLEASE GUIDE & HELP US..........