ATP rating question

I am a furloughed airline pilot. I have been flying as Captain on a 727 for the past 5 years, and lots of time as FO before that.
I'm filling out applications, and have some questions about certificates/ratings in general.

Does the ATP rating supersede all other ratings/certificates? (for instance I don't have a multi commercial...does that mean I cannot accept a job flying passengers in a Baron for hire?)

I do have a SEL commercial rating, so I guess I can do passengers in a Cessna 210 for example.

No where on my certificate says that I have private privileges. Is it assumed that since I have an ATP I can do regular private flying?

If someone asked to see my private pilot cert, I wouldn't have anything to show them.

Also, applications are asking for my certificate numbers for private and commercial. I got those back in the 80's when they used your SSN as your certificate number. For job application purposes, should I list my original certificate numbers for private & commercial on my application (which is my ssn)

Sorry for all the questions, but I haven't thought about this stuff in many years. Maybe some of the younger flight instructors out there will know.

Thanks!

MF