Nick14 beat me to it....I think pretty much all of the subjects have bits you don't "need" to know for the exams. That's not to say that if you had the time, capacity and inclination those segments wouldn't be extremely useful.
Put it in context, the shortest exams are 23 questions (IIRC) yet there is a whole book dedicated to the subject....hence there is a LOT of stuff you don't NEED to pass the exam...the rest just helps round your knowledge a bit better..