Open Graph is an internet protocol that was originally created by Facebook to standardize the use of metadata within a webpage to represent the content of a page. Within it, you can provide details as simple as the title of a page or as specific as the duration of a video.
Yes, implement both to boost engagement. Open Graph is an HTML markup used by social networks to display shared content. Social networks use the OG tags to create rich objects in the social graph. However, Open Graph doesn't provide detailed information about your page to search engines.
Yes, Facebook still uses Open Graph and so do other social media sites like X (formerly Twitter) and LinkedIn.
Adding open graph tags also helps search engines understand your content better. Search engines like Google and Bing use open graph tags to determine what type of content you're publishing. They'll know that you're writing about a specific topic, and they'll index your content accordingly.
Meta Description is used by Search Engines Bots, while the OG (The Open Graph protocol) is used by Social Media Bots, therefore if you want 'extra' information on Social Media sites then you should opt to use both the META and OG tags.