All coaches are different when it comes to raising from drive height. On mine, I can switch from Ride Height to Manual. Then I can raise or lower by three seperate switches. One raises or lowers the front, two raise or lower right and left rear. The coach will raise approx. 6 inches above ride height. It is recommended to travel at a very slow rate at a lower or higher ride height. However, I have accidently driven at a high ride height when forgetting to lower several years ago. Nothing was damaged.
Regarding dirt roads, a 45 ft. Prevost weighs approx 48,000 pounds . If the road is not properly designed, you may quickly find yourself in trouble sinking into the ground encountering wet or soft spots in the road. Engineered gravel roads are ok but stay away from the shoulders.