1. Limited enough. Nice choice, although it's not what I picked.
2. Oooohhh...mirror-curse. Limited in that it can backfire. Also very cool.
3. Yes. But were you planning on getting stuck in a snow monster's cave any time soon? Is there something you're not telling me?
4. To be limited, it would have to be one person at a time and not long-distance. But it would still be fun to see people realize how much of an idiot they are.