No.
An adjective would be used to describe a noun.
'Friendly' is an adjective because you'd use it to describe someone. Any word that can be used to describe someone (a noun) is an adjective.
Wet can be used as an adjective. It can also be used as a verb to describe an action.
adjective
The adjective "open" could be used to describe a mouth that is not closed.
No. It is a noun. It is never used as an adjective to describe another noun.
Hypersensitive it is an adjective. It it used to describe someone.
The word wily is an adjective. It is used to describe someone who is cunning.
Yes, sorrowful is an adjective because it can be used to describe something.
Yes, careless is an adjective, a word used to describe a noun.
The word "decayed" can be used as an adjective or as a past tense verb. In the sense of an adjective, it can be used to describe "a decayed tooth".
The word "many" is an adjective, because it can be used to "describe" a quantity.