1) you can with cheque enclose a covering letter that payment is made under protest . not necessary to be drafted by a lawyer
2) builder has to carry on construction as per sanctioned plans . if plans show flat area as 1350 square feet builder cannot arbitrarily increase area by 140 square feet and demand flat owners pay for additional area
3) the increase is more than 6 %mentioned in agreement
4) as per "UP apartment act 2010" having a builder buyer agreement &
is mandatory, you are supposed to get the
agreement docuement, registered with authority within 4 months of
execution of BBA.& do ensure that builder buyer agreement mentions
"ALL" the details of l of Terms and conditions plus floor plan,
building plan, material to be used, specifications , amenities and
quality to be provided, common area and its use, built up area, carpet
area, date of completion