You can treat 3 areas with coolsculpting just make sure you have a good breakfast or lunch because you will be in the room for 4 hours. Make sure you consult with a board certified dermatologist first.
There really isn't a restriction on how many areas can be treated at a single sitting. However laying still for more than 3 or 4 hours gets a bit daunting. Be sure to consult with a board certified plastic surgeon with experience in all possible treatments of your involved areas. That way you can make the best choice. Remember, if your only tool is a hammer, everything in the world looks like a nail.