As to the question of watching a 1080p Blu Ray 3D standard on a 4K TV, every TV I have seen upscales the 1080p 3D frame packed to 4K for full screen display. Some do it better than others. If it didn't do that you would see a picture 1/4 the screen size with letter box and piller box black...
but is now 2017 i must know when u put a 3d bluray to a active shutter 4k 3d tv what resolution do u get 3840x2160p or 3840x1080p or something els cus passive does 3840x1080p cus gets cut down so one would think a active tv get the 2160p or does it just get 3840x1080p like passive plz help