re 2a: "Cycling merit badge or Ranger Cycling/Mountain Biking elective and 100 miles of cycling" I interpret this as the 100 miles includes miles ridden for the MB. If the Scout follows the mountainbike rather than road cycling they would only have to ride 52 miles so would have to ride an additional 48 miles to meet the requirement.
re 3: "Complete 200 miles of riding activities, including cycling, stock riding, skating, motor boating, mountain boarding, snowmobiling, (including ATV or PWC riding at an approved council program), under the auspices of the Boy Scouts of America, inc