The video for this part (uncomment html) mentions that you can comment/uncomment everything using the shortuct CTRL+"/". This is not mentioned in the instructions themselves.
I was planning on using the videos only if I get stuck, but should I watch each and every video to make sure I do not miss valuable information?
The videos and challenges are made by different volunteers at different times. I wouldn’t be surprised if they often contain some extra tips that can be helpful. If you branch out beyond FCC you’ll find even more helpful advice.
I’d recommend watching the videos after you’ve completed the challenges (unless you are super stuck), since you can always find new techniques and approaches from other people’s efforts.
The longer you spend coding the more you will come to realise there are often many ways to achieve the same thing and many little editor tricks and tips that become useful as you code more and more.