Capital gains incase JDA and share trf before CC

Pratik khilari (CA FINAL) (75 Points)

28 April 2019  
In our case JDA is entered for a land acquired on June 2001, consideration receivable in form of 4 flats. I have sold one of those flats before the CC is received. as per proviso to sec 45(5A) in this case the capital gains shall be taxed when the agreement for trf of one unit is done.

questions

1) what shall be the cost of acquisition?
2 ) what will be the will transfer of land and sale of one unit be seeprate capital gains?
3) shall the sale of such unit be stcg?
4 how can I calim deduction by investing in new plot of land?