Can a dissolving stitch from a cesarean break lose and come through the skin?

Yes. It happens all the time, and in most cases it's nothing to worry about. It can take several months for dissolvable sutures to dissolve completely. Leave them alone if they don't bother you; but if they do, many obstetricians advise cutting them off at skin level. Check with yours to be sure.
Yes but rare. It is possible to be able to feel the end of a suture or knot under the skin after surgery. The knot will usually dissolve after several weeks. It is possible but uncommon for the suture knot to actually come through the skin. You should see your surgeon if there is a problem or opening in the skin.