Why are the cars from the 80s, but everyone has smart phones?

I think it's just for the vibe of the show. Not any specific story reason. The filmmakers like the retro feel of movies they grew up with.

Are there any other companies besides Lumon that exist in this universe?

Of course but why talk about them.


Is everyone in this place where only Lumon seems to exist an "innie" of sorts?

Not a bad question but no