Vat gst on flats

Balasubramanian (Proprietor) (117 Points)

13 May 2018  

390 Villas are being constructed in a site of 24.85 acres. My villa is having super built up area of 2315 sq.ft undivided share of land for him is 1447 sq.ft.
TotalBasic Price quoted was Rs.1,05,79,550.00 @ Rs.4570/- per sq.ft for 2315 sq.ft. Land being registered for Rs.34,72,800.00Agreement for sale of land signed in july 2015.
Construction agreement for Rs.71,06,750.00 signed in July 2015.
Balance 
Booking done in March 2015. payment made so far 
advance Rs. 1 lac on 9.3.15, Rs.22.62 lacs, Rs.48.53 lacs on 30.7.15 Total paid Rs.71.15 lacs.
Builder is demanding final payment with the following Taxes now.
2% VAT on Total Basic Price Rs.2,11,591.00
GST of Rs.9,19,092.99. @ 18%

Service Tax Rs.1,42,403.46
I feel VAT is payable only on 
Material cost.Why the builder is claiming VAT on Total Basic Price ? 
After GST implementation wef 1.7.17 whether VAT is payable by me ? if so how much VAT is payable? I feel if VAT is payable it should be on material cost for construction only proportionately for the amount paid by me before 30.6.17.
how much is the service Tax payable by me . on which amount / at what rate?
Builder says since my villa was completed before 30th June 2017 no Input Tax credit will be given to me which appears to be unfair?I strongly feel I am eligible for Getting on the benefit of Input tax credit if I have to pay GST.
Please clarify.