I have successfully changed the App Icon for the App by replacing the file with the files I downloaded from here.
Its working fine in the Menu with logo and name as expected. but the icon is not changed in the Task Menu.
And in the Menu its fine though.
I replaced [mipmap-hdpi, mipmap-mdpi, mipmap-xhdpi, mipmap-xxhdpi, mipmap-xxxxhdpi] folders with new ones in the android->app->src->main->res path of my project.
Any help will be highly appreciated.