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While typing in  "Latest from ***.com" may trigger some press releases or news sites to show. The Google SERP is not strictly Google News. The Moz screenshot you attached showed Moz's latest blog posts at that time, and were not related to Google News to my knowledge. Hope this helps!

The rel canonical tag to the root of the site could work, but would be better to have a metatag like <metaname="robots" content="noindex, nofollow"> </metaname="robots"> For each page that is developmental and not supposed to be live. This will tell google to just ignore these pages, that they are not ready to be indexed and be part of the internet. It's generally not recommended to do a rel canonical to the homepage, just because it's saying that every page on the developmental site is from the homepage, as well google is still indexing these pages and this could cause issues later on. It's just better to noindex nofollow the dev pages before they go live, since then you can migrate the new to the old and not have some huge issue later on. I send something like this to your private message as well.