You can change the DNS to force youtube in safe mode. That may not block previews in Cortona and Microsoft bing though. A better way would be to run a script in PowerShell (admin of course) to block all of YouTubes domain names in your firewall, works well with windows defender. Alternatively, and not as effective, would be to block it in host files. (Instructions on Google...) However, using a chrome extension is far from permanent if that is what you're trying to do. Alternatively, try Qustodio, it has a free version with customization and is about as permanent as TAG is
Search YouTube blocker on the chrome web store.
Sure you can
Not sure but they can
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