Strange . . . I would have thought it would be an "ihn" vs. "ihm" difference, i.e. the basic structure would be "I will report/notify someone/something to somebody" so "I will report him" would be said with the direct object "ihn" and "I will notify him" ("I will report to him") would be said with the indirect object "ihm", but I see that it cannot be so simple, because "Sie" in you example is in the accusative too . . .
Yes, that is one of the meanings of this verb (specifically regarding the police):
Dictionaries will keep you truer than digital translators will (which are notoriously bad with nuance). :)
When the sentence said "Ich werde ihn anzeigen" I got it wrong and it said the correct answer was " I will reveal you". When I answered this one as " We will reveal him" it said I was wrong as it is "We will report him". Am I wrong or does the meaning change depending on the subject/person?