ExpressJS serving html, android, iOS

I currently have a real-time web app built on the express framework with socket.io. Now, I may have coded myself into a hole here. I need to expand the app to handle requests from mobile devices (android first and then iOS in the future). I am having a hard time finding appropriate guides/examples for the following concerns:

  1. Route separation for web browser/android/iOS
  2. Sending and receiving JSON on an android device
  3. Dynamic layouts based on JSON

I have many questions but hopefully someone has some reading material I can go through before asking aimless questions.

Much appreciated.