Will You please tell me how can i remove COD from a particular product, i want only online payment no COD for a specific product only.

You can install StoreHippo's app Product based COD. To install the app, go to Advanced Settings > StoreHippo App store > Search Product based COD > Install the app.
Once the app is installed, you will be able to select each product if it is available for COD or not through the product metafields.
https://www.storehippo.com/app/product-based-cod