No because you can't fastest.
It is an action verb.
In the sentence that you give, John was faster but Billy was the fastest, there are comparative adjectives, faster and fastest. The verb in this sentence is was. It is not a comparative verb, just a verb. An existential verb, to be precise.
began is an action verb, not a linking verb.
No, "fastest" is not a verb. It is a superlative adjective that compares the speed of two or more things.
action verb because you did this action (sent)
what follows a linking or action verb
An action verb
action verb
Action verb
It is an action verb.
Action verb
The verb stay is an action verb.