Yes. There are many variations of "the prep", but in general you will need to restrict your diet to clear liquids the day before the procedure, and drink a prescribed preparation to wash out your colon the evening before and possibly the morning of the procedure. There may be other instructions for the avoidance of certain foods (seeds) for a few days in advance.
Yes. And most physicians / centers have a specific routine of dietary changes with laxatives, so it is ver important to follow the instructions given to you. One of the most important factors for a quality colonoscopy is an excellent prep.