Cauteloso is the Spanish word for cautious.
No, cautious is not an adverb. It is an adjective, with the adverb form "cautiously."
most cautious
No. it is not. The word "cautious" is an adjective.
most cautious
The adjective cautious has the adverb form cautiously. It means in a careful or cautious manner.
Be cautious out there. You might have some trouble.
Cautious IS an adjective. An adjective is an action!
He was extra cautious driving on the icy roads. She was cautious not to break her new dishes.
The preposition that typically follows "cautious" is "about." For example, "He was cautious about making any hasty decisions."
That is the correct spelling of the adjective "cautious" (careful).
The opposite of cautious is: Careless or Hasty