And the prospective employer can ask anything they want to know.
The previous employer may, in some states, be limited in what they can say about workers comp claims and should limit themselves with regards to medical information.
However, if your question relates to the myth that employers may only verify dates of employment, job titles and (depending on who you listen to) salary, that is ONLY a myth and there is no truth to it. The employer may provide any information that is true, that they have an honest and good faith belief is true, or that represents their honest and supportable opinion.