If you scroll down the page a little bit, you’ll see a full list of every lesson in the course (hint: click on the “Expand All” text to see it all at once).
Is it necessary to go through all of the lessons in order? Nope. I mean, the order isn’t arbitrary, but you don’t need to stick to the order either. Feel free to jump around, and see what lessons are available in each skill, and go with what feels like it’s the most relevant and useful skill to work on at the moment.