TDS on Property 194IA

A)For the first installment how it will be calculated because a part of money was paid earlier as a token/booking amount and no TDS was deducted. Now for balance payment of first installment how will TDS be deducted ?

B)Also TDS is calculated on entire payment to payment excluding GST?

C) There are two buyers and one seller. Payment will be made by either buyers. Will both buyer fill TDS form for each payment or only one buyer paying the installment will fill TDS?