Is motivation an adjective

Answer 1

Motivated is the past tense of the verb, to motivate.

Motivated is the past participle of the verb " to motivate" and can be used as a Participial Adjective.

Example: A motivated student can learn anything they wish to learn.

(here "motivated" describes the student)

So, yes! Motivated is an adjective AND the past tense form of the verb "to motivate."

Answer 2

No. Motivation is a noun. The adjective form is motivated, or for something providing motivation, motivating.

Answer 3

Yes, it is the adjective form of the noun motivational.
Adjective forms of the verb to motivate include motivated.