Comment on BTST/ATST( Buy/Acquire Today Sell tomorrow)
1. On T+3 if exchange can’t find any stock in auction, they will settle the funds in cash. So in these cases, stocks won’t show up after T+3.
2. Even on T+2 morning, there is very small risk you carry like mentioned in point 1. Best to sell only after taking delivery, which is by T+2 evening.