1. There're no plans to build an Android starter kit as of today. Still, as the DX endpoints are the same for both Android and iOS the iOS Starter Kit can be used as a reference.
2. React-Native is a viable approach, pretty much every mobile UI framework should be fine when you plan to use DX APIs directly. You'll find a code sample demonstrating how that can be done with GoogleFlutter on https://github.com/pegasystems/dx-flutter-demo