No, you don't have to complete the courses of the package in a specific order or only one at a time. When you have an active licence all the courses of the package are always available to you and you can practice as many courses simultaneously as you want. You are free to progress in a way that suits you the best. 

Please note that to ensure permanent learning you can't complete a course during a single day. If one of your courses is locked, you can return to it the next day or proceed to another course. Read more here: I am stuck. Why can’t I finish a course?