No, park can be used as a noun and a verb.
Noun: We went to the park today.
Verb: We could not park the car.
Yes, it can. In is an adverb in the sentence "I will go in" although where the person goes "in" (into) is not defined. With an object noun, in is a preposition, and a phrase could be an adverb or an adjective phrase. E.g. I went in the park. The fountain in the park is broken.
No. It is a verb or a noun. The noun may be used as a noun adjunct (like an adjective), e.g. "park ranger" or park bench.
Adverb
Underground is an adverb, as in beneath the surface of the ground. It is an adjective, as in an underground car park
I'm about 90% certain it is an adverb. About can serve as an adverb, preposition or adjective. I'm 99.9999999999999% certain it isn't an adjective as used here, but preposition or adverb depends on whether there is anything more to the sentence: He wandered about (aimlessly) => about is an adverb He wandered about the park => about is a preposition
No. The proper adjective Roman is not used as an adverb. There is a VERY rarely-used adverb, Romanly.
Has is a form of the verb "to have" and is not used as an adverb.
The word "as" can be used as an adverb.
adverb
An adverb is used to describe verbs, adjectives, or other adverbs.
"Seldom" can function as both an adverb and an adjective. As an adverb, it modifies a verb. Example: "She seldom goes to the gym." As an adjective, it describes a noun. Example: "He makes a seldom appearance at social events."
No. The adverb would be "scarily."