Adjectives used as adverbs/ verbs used as adjectives/ verbs used as adverbs

First question: I have been reading English: An Essential Grammar by Gerald Nelson and it gives an example of the words 'hard' and 'fast' being used as both adjectives and adverbs:

Adverb:

John works hard.

Peter drives fast.

Adjective:

John is used to hard work.

Peter drives a fast car.

I was wondering, can all adjectives be used as adverbs in this manner?

E.g.

Adjective:

Small girl.

Are these adverbs???

She is small.

She was small.

She looked small.

Second question: Can present participle verbs be considered as adjectives?

E.g. Are these adjectives or are they still considered as verbs?

The singing lady.

The growing crowd.

The advancing army.

Third question: Can all past participle verbs be considered adjectives?

E.g.

The written book.

The cooked fish.

The bitten apple.

And lastly: Can all past participle verbs be considered as adverbs?

E.g.

The book was written in black ink.

The fish seemed to be cooked.