Gst from builder perspective

Dear Members, I own a small construction business and would like to understand few things about the Input Tax Credit and GST in general.. I am currently going to build a 7200 SQFT property , out of which only 1700 SQFT property is planned for sale. My construction cost is estimated around 1300/SQFT , out of which 60% goes towards material and remaining 40% goes towards labor.. Since, I am doing this construction in Tier 3/4 town so not all vendors ( Labors and Material suppliers ) are GST complaint.. Assume the GST payable from my end on all viable Inputs is 150 /SQFT ( or 10.80 Lakhs) Below are my questions and it would be great to know your advice: 1) What should I do when a supplier or vendors( Material and Labor contractors) don't have GST number ? Do I still go ahead and pay GST on their behalf ? If yes, how can I do this and whether this GST payable amount would be considered towards ITC refund ? 2) Since 1700 SQFT is planned for sale, hence GST received at 12% is 7.2 Lakhs.. My taxes paid to Input material and labor is 10.8 L, whereas taxes received from customer is 7.2 L, how does the ITC math work in this case ? Do I owe Govt or the Govt owes me a refund ? 3) What happens with the Unsold part ( 5500 SQFT), do I owe the GST on this property ? I am unable to understand the math in this scenario - I know that if the Input taxes paid ( say 100 ) are lower and output taxes received ( say 140) are higher than the net amount owed to govt is the difference ( 140-100 =40) .. In my case, the situation is reversed, hence need advice ! 4) Last question : Whether the Govt provides a physical refund (actual cheque ) or its just an adjustment in some ledgers ? Thanks for your time and interest in reading the question .. I look forward to hear from you..