I have never seen a restriction on the class (exempt/non-exempt) of employee. The only restriction I remember seeing for tuition reimbursement at the companies I've worked at was that you must be full time and the coursework must somehow be related to what the company does. That last bit is typically only there to discourage "underwater basketweaving" courses.

The most common degrees people go for seem to be general Business, Marketing, Accounting, and then the more specialized tech. degrees. I'm amazed at the number of CS people I come across who have "silent" MBA's. At my last job I knew at least one person who joined with a high school diploma and eventually had an MSEE all paid for by the company.

It's been available at companies such as UPS for a while: https://ups.managehr.com/Benefits.htm

I'm not sure if it's the norm.

I worked at a FedEx Kinkos part-time for a few months and was eligible. I think it kicked in after less than 6 months.