Variable. People on diet alone or just oral medications may only need to test before and two hours after a meal 1-3 days a weeks or less while those on Insulin need to test before meals, and at bedtime and possibly before and after exercise, during suspected hypoglycemia, and before critical task such as driving.
Depends. It depends on the type of diabetes you have, and the type of medication regimen you are on. Ideally, the more data there is for us to review, the better adjustments we can make. In general, fasting (first thing in morning), 1 to 2 hours after eating, bedtime can all be helpful readings. The number of readings should be tailored to each individual. Good luck!