Not really 4K. It's downscaled to 1080p though. Considering that 4K videos on my 1080p monitor look much better, I suppose it does some kind of supersampling like in video games (?), but that's on PC so not sure if the same would be applied to Android TV but most likely yes.
But why would you?
Fullhd and 4k seems same in a 1080p resolution screen, just data consumption will be more.
How do you get this specification in Sony ?
Use a "test pattern" to verify resolution, example:
For that video on TV that is 4k you will see lines in each grey circle, not a fully opaque grey circle.
Like other comments said if TV is not 4K, then 4K stream is just using more data and not giving any visual benefit.
Yes, every Android TV device will play a 4K video as long as you have the required internet speed, HOWEVER; the video will be downscaled to the resolution your TV supports, some experts say the video will look better than a regular 1080p one so that's an advantage.
Well I can technically stream 4k video on my smart watch, its not gonna magically increase the count of physical pixels available on the screen ofc; but I could watch like that if I wanted, Now please tell me why I would want to do that? ^^
Well you are not really watching 4k, so weird flex but ok lol