Sale of under construction flat and re-investment in new

1. All the installments you have paid would come under LTCG since date of acquisition would be considered date of allotment letter as per Punjab & Haryana High Court decision in case of Vinod Kumar Jain v,. CIT.

But you have mentioned that apartment was not yet completed, then P&H decision in case of Ashok Syal v CIT may apply where it was held that mere construction of room without amenities like boundary wall, kitchen, toilet electricity, water and sewerage connection etc. cannot be held to be house and hence benefit of section 54 cannot be granted. 

2. Brokerage and building transfer fees would be deductible as it was exclusively incurred in connection with transfer.

3. No you cannot adjust LTCG by paying back the home loan because u/s 54/54F assessee should have purchased a residential house one year before the date of transfer and moreover exemption is not available for paying back the home loan. However, you may claim exemption to the extent of Rs 50 lac u/s 54EC by investing in REC/NHAI bonds within 6 months from the date of transfer and you have to hold these bonds for next three years from the date of acquisition. 

Gagan ji, thanks for your reply. Regarding 1.) i.e. under construction flat, the following links suggest that LTCG is applicable for under construction apartments-

https://www.managemytax.in/clients/knowledgebase.php?action=displayarticle&id=642

https://www.business-standard.com/article/pf/date-of-allotment-is-key-in-under-construction-flat-114040500821_1.H T M L

Are there some details that I am missing here ?