1) Yes they are supported, I've just included them to 0.4 because I had problems with them before, now they are working perfectly. And yes there is no limit as long as you are targeting Windows.
2) As long as they are biped armatures or skinned meshes, they're supported.
3) Of course.
4) Unfortunately no, The plugin is designed to load the whole scene at once, then you can do whatever you want to the meshes.
5) Yes, not only that, but you can also overlay the 3D scene to have a transparent background (Autoclear set to Off) and display ontop of sprites. Also, C2 effects can now be added to the scene.
6) I can't show all of them because they are seperated into plugins and behaviours. And C2 behaviours are also supported (ex: Platformer demo).
This plugin is still in developpement, but you can already make games with it, I'll complete the platformer demo to show you and others what exactly I'm talking about.