Yes , I signed the apk. I can install it in mobile phone but in my tablet is impossible.
I suppose that I can't it for version android phone's.
But I'm not sure.
See Feature list comparison for AEM Mobile features .. it should work.
You can't have a phone only or tablet only App under Android but your App should install on either of them.
Your Android tablet or phone requires Android 4.4 or later.
Also make sure you are using the latest 'AEM Mobile Signing Tool', not the old 'DPS' one, you can download it from top right corner of the dashboard when you are in the App section.