Dear Siva,
On first point, a lot of brokers including big ones provide limits and margin without explicitly need to pledge securities. They can be considered as margin when they are lying in the demat account itself when Poa is active.
2nd Question: What I meant was since this 50% cash is an exchange rule, if the client maintains 100% share collateral, Zerodha says that on 50% interest will be charged by Zerodha as Zerodha has to contribute for the cash. But to the best of my understanding now each client’s margin file is uploaded in exchange. So if 50% cash is not maintained, doesn’t the exchange charge penalty, how can Zerodha contribute instead of individual client.