If an employee was involuntarily separated, but is eligible for rehire, how much specific info is the prior co allowed to provide? What questions are allowed to be asked by the prospective employer?

Ex: dates of employment, position, did they leave voluntarily, are they elig for rehire... I as a manager always believed specifics can't be divulged due to privacy issues.

I think potential employers can ask anything but it is up to the previous employer if they feel they should answer.

.I as a manager always believed specifics can't be divulged due to privacy issues.

And you have believed wrong. There are actually no laws that prevent a previous employer from giving truthful info about a former employee. As long as the info provided is factual anything goes.

As a practical matter, employers have refrained from providing too much info to avoid lawsuits.