It does and uploads them regularly unless you disable it.

https://www.facebook.com/help/355489824655936/

Not by default, but they aggressively ask for access to it. It's usually framed as helping you find your friends already on Facebook.

If you explicitly give the app access. Unfortunately, it doesn’t matter. Your contacts may still give the app access.

When I left my previous company, I gave a few coworkers my phone numbers. Within 24 hours they showed up as suggestions on FB.

If you have the app on your phone, or any app that uses their sdk, yes.

Looks like it:

https://m.facebook.com/help/210676372433246