1. Frosting cannot be used instead of powdered sugar, but powdered sugar can be used instead of frosting to decorate the surface of food.

2. There is a certain difference between icing sugar and sugar. Powdered sugar is generally made by grinding white sugar into powder and mixing corn starch and ground sugar. It has many functions, while icing sugar is made by grinding white sugar into powder. It is obtained after processing powdered sugar and is mainly used for sweet decoration.