behavioral
The noun behavior has the adjective form behavioral. (The UK spelling is behavioural.)
unusualsuspiciouswrecklesstimidenthusiasticreticentcourageousaudaciousheroiccautiousmodest
No, you would say - good behaviour and the adjective is well-behaved.
Fearless is an adjective because it is a descriptive word.
As a verb, "explaining behavior" is the act of using words to explain a behavior. As an adjective, "explaining behavior" is the observable behavior in which a person tends to explain her/himself.
Stubborn is an adjective, because it describes something.
The word "ungentlemanly" is an adjective. It describes a behavior or action that is not characteristic of a gentleman.
The word "frantic" is an adjective. It describes a state of wild or frenzied activity or behavior.
annoying, obvious, nosy
The word "erratic" is an adjective. It is used to describe something that is unpredictable or irregular in behavior or movement.
The word "moral" can function as both an adjective and a noun. As an adjective, it describes principles of right and wrong behavior. As a noun, it refers to a lesson or principle taught by a story or experience.
The adjective "mannered" means polite or showing a particular behavior.