Any question may be asked that doesn't violate discriminatory hiring practices (your age, national origin, race, sexual inclination... etc).
Any answer may be given that is true, opinion or honestly believed to be true by the answering party.
There is a huge myth that a former employer can one give your dates of employment, salary and whether you were fired or quit.
That is wrong.
If your former employer wants to mention your personal hygene, your thefts or your attendence record, they may as long as they speak the truth, their opinion or a truth they honestly believe to be true.