The hand-to-hand combat in action movies is chreographed so yeah most of the time the action don't even train in martial arts. Some only do because its a bonus to performing their own stunts.
Yeah sure, if you got the look. Zhang Ziyi (Crouching Tiger, Hidden Dragon and many more martial arts films) is a dancer. No martial arts experience.
Most of them don't know martial arts they use a stunt double, very very few even know martial arts let slone perform them. So yes you can
yeah. You can have a fake fighting style.
Can you be an action star without a fighting style? without muaythai or what ever?