Hi,
JDA does not assume or concur any liability on account of taxation. It is only an understanding that how the sale proceeds or profits from development shall be shared. Actual tax liability shall accrue only at the time of execution of title deeds and receipts of proceeds therefrom.
As such, your answers are as below:
1. No, Capital Gains tax shall be payable only at the time of receipt of sale proceeds or execution of title deeds, whichever is earlier.
2. For you, means the owner of land, the whole amount shall be LTCG only, irrespective of the fact of JDA or Completion Certificate. If you re-invest the amount in another residential property, benefit u/s 54 shall be applicable. But that is only for one residential property and not multiple.
3. No eligibility for further exemption. As you already invested part sale proceeds in another property.
4) In order to fully claim tax benefits, try to sell the house property at once (means all 8 units) and reinvest the same in another property, single only. Please note that the other property should not be again of JDA nature. Else AO may disallow any benefits and may treat the same as your business income. In present situation also, AO may treat the same as business income as you have actually developed the same with another partner. The cost of units retained by the builder may treated as your cost and 8 units as your sale price.
Regards,