Section 1: It was so long =(
Section 2: It was so short =D But that time I could have used to go back to section 1 =(
Section 3: Too easy. Pattern recognition ftw.
There were a lot of 3x3 pictures were the first picture plus the second one equalled the third one. Or superimpose the first one over the second and the ones that overlap cancel.
For the put in order and choose the middle ones. The easiest way is to either assume the pattern is a combination of rotation, translation and reflection (plus colour swapping) and try to eliminate two straight off. For example, if you notice there is a ball in all of the pictures that is always either white or black, and there are three whites and two blacks, the pattern is almost always going to be white black white black white. So the ones with black on them can't be the middle one. Then you work from there, try and figure out which is first and last (Most horizontally left... sequence of rotations etc.). Meh, that's just how I did it.