Exemption in Sec. 54 F on amount incurred prior to sale of original asset.

(a)I have booked a flat in ₹40 lacs in Feb 2015. And agreement made in Feb 2016. (b)The date of completion of project as per my agreement was in Approx 30 months I.e, in August 2018, but the project is still ongoing and God knows when it will complete. (c) I have made a payment of ₹10 lacs in the year 2015 before agreement and 20 lacs from 2016 to 2017 from bank loan. (d) In between I sold a land in June 2018 and arising a Capital Gain of ₹15 lacs. (e) I have paid Rs 6 lakhs in May 2018 and Rs 4 lakhs in July 2018 from my side. Now these are my Questions: 1. My LTPG is ₹15 lacs, can I get full exemptions under 54F as I have invested ₹20 lacs from my side towards construction of my flat. Though, it is yet to complete. 2. If not, can I get exemption on ₹10 lacs which were invested by me just one month before & one month after selling of my land and can pay Income Tax on left over amount (LTPG - Proportionality Amount Invested) which may be 20% of ₹ 7.5lacs.=1.5 lakhs Thanking you.