If there are 2 sizes of the fountain beverage you can ask for either size.
Slushies and smoothies are not the standard fountain beverage so you'll have to ask at each CS if it is included, but probably in most cases it will not be. Likewise you'll have to ask if it is a dessert option and again that is dependent on the CS. If it has the purple dining plan next to it, however, you can purchase it with a snack credit.