Hello there.
To answer the questions at the end of your post - Why should you read the whole text instead of a chapter or section - Well, the goal is to really create new neural connections and associations. Exposing your brain to the entire text helps to lay down the tracks for more complete information processing, not just fragmented pieces of information.
Now you may only need to use certain sections to fulfill on your assignment, and that's cool, and yet, you never know when some of that other information may be required, relevant or useful to you in the future.
Having at least created some level of awareness and familiarity through the PhotoReading process will serve you in the long run.
Yes you can very well just PhotoRead sections, and I'd suggest that you stick to the system. It is easy to do and once you get used to it as a part of your study habits, it will be second nature.
And, there are side benefits which you can only experience as a result of "doing the thing." Emerson said, "He who does NOT the thing, has NOT the power. He who DOES the thing, HAS the power."
And remember NOPS! Notice it. Own it. Play with it. Stay with it!
