how many stocks are allowed to get the OHLC data at the same time?

I am not using a Postback URL for my app, as my app is not deployed anywhere yet. However, I am using the instructions mentioned at https://github.com/zerodha/gokiteconnect?tab=readme-ov-file#api-usag

For end-points rate limit, go through the documentation here. Since I'm using this to calculate pnl and plan on doing it every couple of seconds,

API rate limit

Our kiteconnect system is reliable and used by 1000s of developers, including a lot of start-ups. 429 - TooManyRequests

Could you enable the debug logs as per the getting started guide here? This will show what the API is actually responding with.

Will both machines be able to place orders simultaneously or will one get logged out?

You can refer to the documentation for api rate limits.

The rate limit is per API key. There is order related restriction per client id, go through the documentation here.

Go through the API rate limit here.

Reference : https://kite.trade/docs/connect/v3/exceptions/#api-rate-limit

Go through the rate limits here.

You can run multiple instances but within the API rate limits defined here.

kiteconnect.exceptions.NetworkException: Too many requests

Can I call my Zerodha api from two machines , simultaneously ( within the API usage limits) ?

while fetching order details - couldnt get the order id

Go through the rate limit here.

kite = KiteConnect(api_key="###my_api_key") #api key , access token and secret key is in string..!!

Does that mean I can create any number of KiteConnect instances without limitations?

Go through the rate limits here.