I'd like to know if Netflix or YouTube is on the Apple Watch
How should something like that go? I know about 0, but it sounds illogical
No. The screen is far too small and the battery would be empty in no time. For such applications smart watches are not made.
How should something like that go?
Screen = watch video
Yes, but the screen is far too small for that, or is the technology already there?
? I have a 10-year-old car radio on which you could already watch movies, if he has swallowed the format.
Technically, of course, this is not possible so far, at least there's no compatibility for this.
Is a car radio as small as an Apple Watch? NO. A car radio is 5-10 times bigger
Yes - today, the display of said device was about twice as large as that of an Apple Watch. And that was a lot for those days.
You can play a movie on any display, even if it's only 2mm, why should not that work? The question is how much you have as a viewer of it.
It does not work for a watch, neither on an Apple Watch nor on my Fitbit Charge 3
Yes, but that is not due to technical limitations (on the Apple Keynote has been shown several times, how movie sequences on the Apple Watch run) but because of the fact that simply no software is available. If there was a YouTube App for Apple Watch (why they do not exist for a variety of reasons, and certainly that it makes little sense to watch YouTube on the Watch), that would work.