Is it acceptable to reheat frozen food?
If you mean like a potpie or a TV dinner? Yes you're fine, go for it. 

If you're really worried about it here is the rule. (been a few years since I took serveSafe)

When reheating foods you want the internal temperature to reach 165 degrees F. (74C) for 15 seconds. In practice (at home NOT at the restaurant) just get it nice and hot.

Note: Homemade foods generally need to be carefully reheated but not frozen dinners etc. They cook them pretty good at the factory.