As to 1- probably, because he does not want your bowels slowed down. You will be taking laxatives to prepare and bowel slowers kind of defeat the purpose of cleaning out the bowels. You want a clean scope.
2) I have been told to stop taking all solids after noon the day before the scope
3) have no idea what Klean-Prep is. I drink a clear-colored bottle of Magnesium Citrate the night before and take a Fleet enema 2 hours before leaving for the procedure the day of, and it does the trick.