Now I'm not sure if you are allowed to re-enter after your interview before your case is decided/you get the visa but I would imagine so (if have valid visa), you would just need to exit again to get the visa later.
I believe the issue with what you're describing is that if you're on a temporary visa, like a student visa, applying for a green card shows intent of immigration so you cannot return to the US on a student visa.
If you have an H-1B already you may be able to do what you're describing. If you're a recent grad in the US this basically locks you out of trying to get a green card until you've already secured an H-1B.
False
You don’t need a job to apply for green card.
Valid visa, yes. But that’s easy.
> don’t know how this will play out for employment based categories
I am only talking about employment based categories if you refer to my original comment. I’d be curious to know what visa categories allow you to file for an employment based greencard without a job?
In practice, though, almost all employers file EB GC petitions for only their current employees, not future ones.