Your service is currently using Apache (not IIS), I'm guessing you are proxying back to IIS. Your server chain is the android compatible one, so it should work fine for both iOS and Android.
If you skipped the Apache proxy you would indeed have problems with older Android devices becuase it's difficult to serve the android compatible chain on Windows (IIS) So.. It's impossible to support Android 7 and older on IIS? (In a non-hacky way?)