For those who are wondering, even after 10 years (lol), option to hide Favorite playlist is still missing for some people.
Actually, I found out it was depending on the language you are using on YouTube. It's crazy.
So all you got to do is switch language to English (US), then go to your playlist, show it all, then you'll have the private option showing.
Since you are communication using a web-connection you need a ip-address. Ip addresses are usually not anonym because they are bound to a contract. There are some restrictions: You could use a web-cafe for example and use this way the ip-address bound to a contract of the owner of the web-cafe.
Since slack is using TLS you have "some&...
If you want to use P as the reply author, be sure to be signed in the Chrome Web Store as P. Please note that P should be a Google account. If you want that certain name be displayed as the post author, set it as your Google Account name. For details see Change your Google Account name & other info
The above because the posts in the Chrome Store, either ...
I don't Think so. What you can do is mark your video as unlisted and then share the link with the people you want to see the video. However, What you want can be done in vimeo, check there website for details.