first answer: You don’t have to flip your fabric over, just flip the individual patterns. so the white ones will be with the pattern right side up and the shaded will be the patterns right side down. They do this so they can lay the pattern pieces a certain way and get it to all fit with the same fabric amount.
second answer: the difference of 3a and 3b is just a different layout based on the width of your fabric. If the fabric you purchased is 44/45″ in width than you follow the layout for 3a. If it’s 58/60″ in width than you follow 3b.
Hope this helps and good luck!