2) A problem. Sometimes OK, but others not.
3) Turning off the lights is just cutting off it's electric supply. No real Melachah. (On Shabbat we wouldn't do it, however). Putting on a light might be like making a fire. We are expected to make our lights and fires before the holiday. If however, we did light them and they were inadvertantly extinguished, we can relight them on Yom Tov.