If I lose 20lb what will go first? Some fat all over or belly and butt?

Sorry- can't predict. That wany certainty. Spot fat loss does not occur naturally. By losing weight in general some will probably be in areas that you desire. But, we don't get to choose what area of body fat is lost from. Eat healthy ; be physically active. Calories burned must > those consumed. Engage in regular aerobic exercise (i.e., running, swimming, nordic track, bicycling, kickboxing, walking, cross country.
Depends. The area of fat loss would depend on your age, diet, muscles exercised and genetics.
All over. not determined by nature of diet or specific exercises.