On does not have an adverb. It instead is a preposition. A preposition is a word kinda like a verb but where the object is held.
E.g The chair is on the rug.
Correctly is the adverb in that sentence.
That sentence does not have an adverb.
Subject of the sentence Verb of the sentence Adverb of Manner Adverb of Place Adverb of Frequency Adverb of time Purpose
"Is" is the verb. There is no adverb in the question.
Correctly is the adverb in that sentence.
The adverb in your sentence is 'thereafter'.
The adverb of the sentence is quickly.
The adverb in the sentence is "very," as it modifies the adverb "quietly."
The adverb is late.
The adverb in the sentence is "seldom," as it describes the frequency with which he did poorly on tests.
The adverb in that sentence is downstairs. It's an adverb of place and tells where you ran.
The verb in "It has a long nose" is has. There is no adverb in that sentence.