I don’t know what you mean by ‘two groups’. If you are referring to the revision lectures, then these are meant as just quick revision after you have watched the main lectures and finished your studying. The main lectures use our free lecture notes – these lectures are a complete course for Paper F3 covering everything needed to be able to pass the exam well, and need to be watched with the lecture notes in front of you.
I do suggest that you watch our ‘introduction to Paper F3’ video, which is linked from the main F3 page.