A:Answer Only if you have a supported device like XBox Pro, PS4 or Apple 4k streaming device. These devices have build-in tests that you can run to the TV and it will tell you which features are supported (or not).
Also, if you have Netflix, it will detect your 4k TV and prompt you for the plan (if you don't have it). You can do search in Netflix for "4k" and it will list those shows and you can stream it. During the stream, click on the 'Info" button and it will show the resolution.