Question

1. To what extent are you concerned?
2. I am concerned about the matter to the full.
3. I am concerned about the matter on a small scale.
[Are the answers correct? The propositional phrases at the end are adverb phrases, aren't they?]

Answer 1

In #2, I'd write "... to the fullest."

Yes, in these sentences, the prepositional phrases are adverb phrases.