I am new to Xamarin Forms and I am working with VS 2015, this download the android SDK automatically, what is not clear to me is how to know when I start working, what versions of android is my application functional ?. .. that is to say I test the application on my cell phone that is Android 5 and it works fine, but it would also work for Android 4, Android 6 and Android 7, and how to develop on these platforms ... Thank you very much.