Capital Gains on sale of redeveloped flat by NRI

I filed my returns for FY23-24 wherein I claimed exemption us 54 for capital gains on redeveloped flat. I provide below some key dates and questions: Confirmation Deed between Builder, Society and me allotting flat No.10 is April 10, 2023 Part Occupation Certificate was given to Builder on August 10, 2023 Occupation Certificate given to Builder on November 9, 2023 Possession Letter is dated April 4, 2024 1. I understand that the capital gains exemption us 54 will be revoked if I sell the redeveloped flat within 3 years from date of purchase of a redeveloped flat. Are the 3 years to be calculated from date of allotment (April 10, 2023) or date of part occupation (Aug 10,2023) or date of occupation to builder (9/11/2023) or date of possession (4/4/2024). Note the possession was delayed only because we couldnt travel to India though the occupation certificate was given to builder much earlier. 2. I understand indexation is not available to NRI effective an amendment in July 2024. For FY23-24, we did avail of exemption us54 where the cost basis was indexed to arrive at exempt capital gains. I assume if we hold the flat for 3 years, the previously exempt capital gains are still available to us as NRI, even if they were based on indexed cost basis?