Long Term Capital Gain on ready to move flat

I booked an under-construction flat at the cost of approx 1 Crore in Nov 2021. I have allotment letter dated Nov 2021. As of today, the offer of possession has been made by the builder and now I have paid ALL the amount to builder i.e. 1Cr. Flat registration is not yet done and physical possession not taken YET. Now, if I intend to sell the flat. Let's say I sell the flat for 1.50 Cr. My query is : 1. Will long term capital gain be applicable as the 2 year is passed from date of allotment ( property is no more under-construction and as per latest amendmnets for an immovable property holding period is 2 years ) and my agreement to sale would be somewhere in Nov or Dec 2023 ? 2. Assuming the sale price to be 1.5 Cr, I am assuming that I can calculate the indexed cost based on the date of actual payments. Long term capital gain will be the 1.5 Cr minus the Whatever the final indexed cost turn out to be. I will then be able to claim exemption on this long term capital gain under Sec 54 by reinvesting in another residential property. Right ?? 3. Also, is there any limit overall beyond which one can't claim Sec 54 exemption on long term capital gain ?? Can one claim the Sec 4. If for some reason, the long term capital gain is NOT applicable then till what time I need to wait to ensure that it becomes available.