Tds on flat when builder has raised the cost on last demand

I booked a flat with a builder in 2010 with total cost of INR 45 Lakhs. Few installments were paid after 2013 when the 1% TDS rule came into force.

In Jan 2018, the builder has raised the cost of the flat to 53 Lakhs citing increase in area and other factors. This is the last demaind from builder.

Now I am liable to pay the 1% TDS. So far I have not paid any TDS since the cost was less than 50 Lakhs

My Queries:

# I suppose I have to pay TDS on all the payments after June 2013. Please confirm

# While filling the form 26QB what amount should I mention for the payment made: the amount of the final demand or the total amount paid after June 2013. The web page accepts excactly 1% of the payment done as TDS

# Will IT Dept ask me to pay any penalty of late deposit of TDS. I am not at fault since the price of unit increased in the last demand issued this year.

Thanks