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I see this as good news. Sites break and pages go missing (according to Google's crawl) from time to time. I was concerned at first that permanent redirects were added by mistake. I would give it some time and default to Google's usual advice for fixing 404s - which is to just fix the error and monitor in search console.

Yes, you can return multiple rich snippets for the same query. With SERP features, there are also several different ways to appear on the SERP for the same query. Videos, Photos, Q&A's, etc. Your mileage will vary based on how well you rank for the term, the features that are currently present, and your sites authority on the subject.

Hi, Occasionally you might see Google does this where they will return a URL and as part of the description, show a hashed anchor - but they won't show just an anchor as a result in its own right. It will always form part of the page that Google returns. Worth doing if you think it might help usability but it wouldn't fit for every page and circumstance. Have seen it used to good effect, but am seeing less and less of these. -Andy