I cannot see the pattern so I'm answering blind ...
Question 1.) you could work it the way you say - or
you could k2, p2, k2, then 6 stitches in garter , then k2, p2, k2, six sitches in garter.
or you could k2, p2, k2, p2, k2, p2, k12
(I can't see what the pattern is so can't tell you which would be most logical.
Question 2 - the reason they say that is that on the return rows, you will knit the garter stitches, but the rib stitches (the k2, p2, k2 section) you will purl the knits and knit the purls.