12
No, there's no such thing or concept in Stack Exchange.
Once you post question or answer it's public to everyone. You can delete it under certain conditions, but even then any user with 10k reputation and any moderator will still be able to see that post.
In extreme cases, moderator can "hard delete" a revision, aka redact it, see What should I do if a ...
8
No, you cannot make them private. By posting content, you have agreed to the Terms of Service, which state
Subscriber Content
You agree that any and all content, including without limitation any and all text, graphics, logos, tools, photographs, images, illustrations, software or source code, audio and video, animations, and product feedback (...
Only top voted, non community-wiki answers of a minimum length are eligible
