It would depend on the context. If you were only talking about how a person looked, then I agree with Gabriel that there is no antonym, as you are simply stating a fact. However, it could be used in a situation that implied that what we see is not necessarily true. In that case, 'in actuality' would be the phrase which means the exact opposite. "He was calm in appearance, but in actuality, he was in great fear."

The Antonym of Appearance would be, as Frank indicated, Actual or Actuality. Things which are "apparent" may not actually be fact. Example: A man might show a lot of money in his wallet when in a restaurant with his friends. However, appearances can be deceiving. The man might not be wealthy at all, but merely being extravagant to put on a show in front of others. .

Right. Depending upon context consider: in conclusion, upon departure, in the end, upon exit, in absence, upon disappearance, upon leaving.

inwardly internally inside means hidden not in sight

I don't think the phrase has an antonym, hana. You might find this when describing the appearance, for instance: "He was handsome/ugly in appearance"