With most stem plants you can cut anywhere and replant as long as the cutting has at least 2 nodes and some leaves. Burry the stem to the first node and you should be good to go.
Yep, just cut where you want it and bury it in the ground. I leave the last node on so the leaves will act like a platform so more sand can get on it, making it harder to uproot the plant. I usually discard the plant that the trimming came from unless if it has a baby plant growing from it.