Injecting JS code into Webview via loadurl differs in behaviour depending on Webview version and place of injection

Question

Background - We use Grafana to show some data on app in a webview. But Grafana is not supported older version of webviews hence we decided to inject a JS code to detect if Grafana can be run on this version or not and generate corresponding event. On some webview versions I am not getting the callback at all but on some webview version I can get the callback only if I inject the script in onPagestarted.

Following are two places where I can inject JS code either in onPageStarted or in onPageFinished. Both the place same JS function is injected(EVENT_HANDLER_JS).

    binding?.viewWeb?.webViewClient = object : WebViewClient() {
        override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
            super.onPageStarted(view, url, favicon)
            binding?.webProgress?.visibility = View.VISIBLE
            binding?.viewWeb?.loadUrl(EVENT_HANDLER_JS)
            eventCallback?.onPageReloadStatus(PageReloadStatus.Loading)
        }

        override fun onPageFinished(view: WebView?, url: String?) {
            super.onPageFinished(view, url)
            binding?.webProgress?.visibility = View.GONE
            binding?.viewWeb?.loadUrl(EVENT_HANDLER_JS)
            eventCallback?.onPageReloadStatus(PageReloadStatus.Success)
        }
   }

But in older APIs(27, more dependent on webview version than API level) injection in onPageFinished is not able to invoke the JSInterface.

const val EVENT_HANDLER_JS = "javascript:(function() {" +
    "function receiveMessage(event) {\n" +
    "$JS_INTERFACE_NAME.receiveMessage(JSON.stringify(event.data));\n" +
    "}" +
    "window.addEventListener(\"message\", receiveMessage, false);"+
    "})()"

The problem with injecting into both places are that events are recieved twice in the JSInterface(In newer API).

Is there any way to

1. Know about different behaviours of injecting JS into onPageStarted or onPageFinished functions(I feel like the postEventMessage from JS side is not finding the correct object(window.parent or something))
2. Any way to avoid injecting JS if it's already injected?