anyone has intraday banknifty options data or knows a website where the strategy can be backtested on intraday
I know no such platform. If you find something at all, you should raise lots of questions before you take the results to be reliable. Backtesting a particular option instrument is ok. But when it spans multiple expiry dates and strikes, option backtesting is hard. More so for fixed strike markets (like banknifty).
In my last bank, we developed an option backtester. It worked because it was geared towards swaptions market - an OTC vol markets. This market (and a few others like OTC FX options) trade based on fixed delta. Backtesting such options markets is relatively easy. You can produce reliable results (including trade fill, trading cost and price impact) by fitting a vol model and running backtest on this fitted vol surface. This accuracy is hard to replicate for fixed strike markets, as a vol model approach like above does not work as good.
At blueshift, we do have banknifty (and all F&O) options minute-level data. We have not made them available on the platform as we are still to find a methodology that is accurate enough to rely on the backtesting results. We have a few features in the pipeline and this is one of them. So keep an eye out for them.