Knowing any material by heart is going to make it faster to get things accomplished. But fortunately, software development is a lot more like composing a musical score rather than performing it. You can take all the time you need, and you鈥檒l just decrease your development time as you gain experience.
Knowing that you can understand what you鈥檙e learning is important, but it鈥檚 also important to be able to find the information that you鈥檝e learned, later, so you can study it again as you need to. Fortunately, search engines have made it so that we don鈥檛 need to take as copious of notes as we used to, in order to retrieve information in the world, but there鈥檚 still going to be a balance of mental cues, and a bookmarking system of some kind, that will be optimal for each individual. The trouble with telling you exactly how to do that is that it will be a unique mix.
In terms of the content on our site, feel free to explore in any order you like. We try to structure things so that they build on each other, but if you鈥檙e new to what we teach, you should expect that if you were to get through a lot of episodes, and then watch them again in order, that you鈥檇 understand all of the earlier ones better on later viewings. You鈥檒l learn a lot just by being immersed, seeing concepts used in many contexts, even if you don鈥檛 understand them as well as you want to. You can think of it like living in a foreign country without being a native speaker of the local language.
Good luck and have fun!