1) builder cannot alter the size of flat without flat owners consent
2) your agreement provided for purchase of 1030 square feet flat .
3) if area has increased by 10 square feet builder shroud not charge flat owners extra amount
4) Section 7 of the Maharashtra Ownership of flats Act laid down as follows- After the plans and specifications of the building, as approved by the local authority as aforesaid, are disclosed of furnished to the person who agree to take one or more flats, the promoter shall not make – (i) any alteration in the structures described therein in respect of the flat or flats which are agreed to be taken, without the previous consent of that person; (ii) any other alterations or additions in the structure of the building without the previous consent of all the persons who have agreed to take fiats in such building.
5) file complaint against builder before consumer forum and seek orders to direct builder to deliver vacant possession of flat , OC