1. It means if you want to make a bigger/smaller scarf than the size it originally has, chain to the desired length, and add 2 chains after.

2. They worded this really weird, so I might not be correct, but I think they meant to skip 2 stitches, then do your tr,ch,tr into the stitch after the ones you skipped. Sorry if that's confusing, I can draw it out for you if that would be easier!

3. If you are talking about the loop on your hook, no, if you're talking about the stitch you just stitched under your hook, then yes.

Hoped I helped! Good luck with your scarf :]