You can refer to the documentation here.

Yes, you can use WebSocket streaming in FULL mode.

You are sending the wrong symbol format, it should be exchange:tradingsymbol. Go through the documentation here.

You can fetch OI using quote APIs or WebSocket streaming.

https://kite.trade/docs/connect/v3/market-quotes/#retrieving-full-market-quotes

https://kite.trade/docs/connect/v3/market-quotes/#retrieving-full-market-quotes

https://kite.trade/docs/connect/v3/market-quotes/#retrieving-full-market-quotes

https://kite.trade/docs/connect/v3/market-quotes/#retrieving-full-market-quotes

https://kite.trade/docs/connect/v3/market-quotes/#retrieving-full-market-quotes

You can use the full market quote, it has timestamp field.

Can I get history of circuit limit?

The full Instrument list is used for instrument info like instrument_token, trading symbol, etc but not for live market data, so market data like last price, won't be able on full instrument list.

Do we have any api that I can use to calculate margin required for any particular trade

Yes, you can fetch up to 500 instruments in one go.

if any API provide Market Capital

Is there any method using which I can check If a stock had hit lower/upper circuit on a specific date?

In the OHLC Quote, add a field for date

@DS4769 Can you confirm that you do not provide expired options data?

@VarunAgw

@aatishg