The adverb forms are sadly and cautiously.
No, cautious is not an adverb. It is an adjective, with the adverb form "cautiously."
The adjective cautious has the adverb form cautiously. It means in a careful or cautious manner.
The adverb form is "cautiously."
No. Sad is an adjective. The adverb form is "sadly."
cautious
Yes, there is. The adjective sad has the adverb form "sadly."
sadly?
Yes, it is an adverb. It means in a sad, tearful manner.
As an adverb, "creep" means to move slowly and stealthily, typically in a cautious or furtive manner.
No, it is not an adverb. Saddened is the past tense verb (and past participle) of the verb "to sadden" (make sad). The seldom used adverb form is saddeningly.
No. Unhappy is an adjective meaning sad. The adverb form would be unhappily.
No. Caution is a noun. To use the -LY suffix, add it to the ADJECTIVE form (which in this case is cautious) and you will form the adverb (cautiously).