Presenter
Town crier, mayor or council.
no
A passenger? a vehicle user?
The person is a blackmailer.
A knowledgeable person.
a person
A person?
There would be a number of names a person could be called. The primary one would be competitor. However, it could be skier, bobsledder, or ice skater.
You call that person a scholar.
an ally
You would call them someone who peruses.