Adverbs

determinatly

The adjective is harmonious and the adverb is harmoniously.

Yes, because it describes how you do something.

No, it is a plural noun, or less commonly a verb (form of 'to key').

The singular noun key is also an adjective, but it has no adverb form.

When, To what extent, How much, how, why

proudly

It depends on what it is modifying, a noun or a verb. It is usually an adjective.

Nearest is just the superlative form of the adjective near. But like some other adjectives, the comparative forms can also function as the comparatives for the adverb (nearly).

e.g.

The nearest star (adjective)

The new houses were built nearest the cliff (most nearly, adverb)

exactly

Harmonically

The adverb form of the adjective confident is confidently. It means in a confident or assured manner.

1. examlpe of adverb of duration

Usually

Nightmare is a noun.

Nightmarish is the adjective form.

Nightmarishly is the adverb form.

yes, You could say she magically raised her wand

scientifically

No, it is an adjective meaning 'suggesting caution' in doing certain things.

The adverb form of the adjective close is closely. It can refer to physical proximity or resemblance (closely spaced, closely related) or to careful attention (watched closely).

Seen is not an adverb, no.

The word seen is a verb.

The word "cunningly" is already an adverb. It is the adverb form of the adjective (or noun) cunning.

One of the adverb forms is productively (there is no adverb producely or producibly).

They are words that modify the verb and indicate how often an action takes place.

because you could get in a crash and die.