Title.
Title.
They should make it available for android tv. One of the best android tv box is the nvidia shield which already come with a controller would be an easy in for them to get a million controller enabled devices from the very start.
No one knows for sure right now, its too early and not enough details.
Totally guessing however id expect google would want this to be on as many platforms as possible, i would be expecting a deticated AndroidTV app.
Absolute worst case scenario, its going to be available on android phones and tablets, it will probably be sideloadable
No info about that yet. My guess is it'll come in the form of an Android app that's compatible with Android TV as well as a Chrome application or extension (maybe just a website).
They never mentioned ATV, at all
It should be native, although considering the "semi abandoned" state of Android tv i wouldn't be surprised if it won't be supported
i'd guess since android tv's have chromecast built in, it would be native.