This is called Scroll To Text Fragment, and arrived in Chrome 80.
Here is the draft specification, and the original proposal.
It seems to me that this is another feature that Google just added to Chrome without other browser vendors signaling any interest (like Portals, though that one never graduated from being a flag). Here is an article that calls Scroll ...
There are two important points around URLs that are relevant:
Keywords in the URL don't matter much at all for SEO right now. Having the year in the URL isn't going help you rank better.
Stable, unchanging URLs are best for SEO. Having the year in the URL makes you change the URL every year.
Having the year in the URL is not good for SEO. This is a ...
If you are going to use a slash (/) in your URL, you should have content when the URL is truncated to that point. A slash in the URL commonly represents a directory. Both users and bots often shorten URLs to the slash looking for an index page.
An alternative is to use dashes: /post-best_funny_videos-dkKE_wd3jJ. Dashes are not commonly understood to ...
I can't see anything wrong with serving a 404. After all, there is no content at that URL.
The only other option would be to "redirect" to the correct URL, but by reversing the order of those path segments and having the slug first, that may be tricky, unless the slug is guaranteed to be unique also (in which case you wouldn't need the ID anyway).
Yes, a 301 redirect would be the way to go about it.
According to yoast,
Use a 301 redirect to permanently redirect a URL to a new destination.
This way, you tell both visitors and search engine crawlers that this
URL changed and a new destination is found. This the most common
Via - 6 questions about redirects for SEO | Yoast