One entree or combo meal, one non-alcoholic beverage, and one dessert. No separate sides. If the fries come with the burger, it's a combo meal and they are included. If the fries are sold and priced separately, they are not included. There are some combo meals in a few places (Pizza Planet is one) that do include the salad as part of the combo. But the general rule is, if the side is priced separately from the entree it is not included. You may be able to use a snack credit to add some side dishes.
Breakfast does not include the dessert. No substitutes, you just give up the dessert allotment if you use a QS credit for breakfast.
If the CS serves milkshakes (not a whole lot of them do), they MAY allow it as a beverage. It's up to the restaurant. Coffee, tea, soft drinks, milk or bottled water are usually permitted as beverages.