Some questions about this project

Hi,
Can you please provide some examples of adding Geojson files into map?It seems there is not any api help for this great project.
Also Is there any access to Threejs stuff such as scene and renderer, etc?

An my last question is about its support for 2d canvas. Does it supports for 2d canvas?as we know that webgl is not supported in some old browsers.

Thanks very much