Android - Facebook Analytics App Install Event not triggered

Question

Am using Facebook SDK 3.21 for Android and Facebook SDK 3.23 for iOS, and I have an App ID & App Link url.

Now my questions are:
1. Is App Install event counts for each fresh install to the same device.?
(By fresh install I mean installed once, launched the app & uninstalled it. Again installed and so on)

2. I tried fresh installations for 3 devices; Galaxy S4, Galaxy A7 & Moto X. The App Install event is not getting counted for Galaxy A7 (not listed in filter options). And If I freshly install it again to 2 other devices, the app install count is not getting updated. So is there any special case like for a device only once the app install event is counted? But in case of iOS app, fresh installations are counted as each App Install events, and so the count keeps updating. But iOS device models are not listed in filter options. (During upgrade installation, the app install is not counted which is expected)

Android code:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    AppEventsLogger.activateApp(this, FB_APP_ID);
    Settings.sdkInitialize(this);
    Uri targetUrl = AppLinks.getTargetUrlFromInboundIntent(this, getIntent());
    if (targetUrl != null) {
        Log.i("Activity", "App Link Target URL: " + targetUrl.toString());
    }
    ........
}

iOS code:

- (void)applicationDidBecomeActive:(UIApplication *)application{  
    [FBSettings setDefaultAppID:FB_APP_ID];
    [FBAppEvents activateApp];
}

3. Now in Android, if I use the AppEventsLogger.activateApp(this, FB_APP_ID); in onResume() function (as per documentation), and Settings.sdkInitialize(this); in onCreate() function, the App Install count is not updated for fresh installs but Inbound AppLinks count updates(on clicking App Link shared in Facebook). Now if i remove the Settings.sdkInitialize(); from onCreate(), the App Install counts but not the Inbound AppLink event. I can't figure out whats happening here.

4. Can we track the Installations done via App Link(doesn't include installations directly from play store)? Is there any event for that.? What I came into conclusion is that, Mobile Ads Installs could be tracked but not via App Link(If am wrong please correct me).

Final note, the AppEventsLogger.activateApp(this, FB_APP_ID); updates the App Launch events as expected and i haven't used AppEventsLogger.deactivateApp(this, FB_APP_ID); as I don't want any session events.

I'am out of my mind, any help will be appreciated and thanks in advance.