IEX is a share of an exchange similar to BSE but the only difference is that IEX has a different instrument to trade on its plat form. they generally let electricity producers and electricity conumers(usually big insustries) to exchange electricity or green certificates on it’s platform. so as far as my knowledge it is not serving to us/common man, but it is more for a industrial purpose. so the answer to your question is very simple. zerodha or any other borker can not work with them as IEX is not stock or commodity exchange and the target audience is different so you can just invest in the stock but not trade on it’s platform.
In the case of IEX, interest earned is as a result of IA and not OA.
If you had observed the Cash-flow statement from the start, you would have noticed that certain adjustments are being made to Net Profit. These adjustments are carried out, to ascertain cash-flows from OA.
Since, interest earned is from IA, the same is first excluded from OA and then disclosed under IA.
Also, while 268.34 lakhs is the interest earned for the year, 598.24 lakhs is the interest actually received during the year.
(For example, you have a 5-Year FD which pays interest of 1 lakh every year, but the interest is paid only at the time of maturity of the FD (cumulative). In this case, while you earn 1 lakh every year, you do not actually receive anything till the end of the 5th year).
We can cross-verify / reconcile these interest figures as well. I have attached the screenshot for your reference.