Maybe, according to the "warning" on your screenshots, your
device is "too small" to display the full "desktop" view.. that's
why the preview might not be "accurate"? 🤔
I won the "Event Spriting Contest"
as it says on News Announcement #224.
Yes, because when it is parsed by the server and not by your
browser in the live preview, it's a little more tolerant of errors
(the other problem that I mentioned - failing to properly open and
close tags hierarchically, for example - is also tolerated better
in the final parsing). But it's still an error after all and should
be avoided. It is not guaranteed that the server parsing accepts
these errors forever, so it's always best to stick to the official
documentation as closely as possible.