After a quick Google search, it appears that you can over clock through the BIOS on this board. You must have missed it.
To answer your two questions;
1: Yes.
2: It depends on what your shut-off temps are set to in the BIOS, and if you have it enabled.
Over clocking through Windows isn't a very good idea. For one, if you go too far, it's a PITA to fix it (if you have it set to automatically run on startup).
Plus, every time you restart your machine it is changing the clocks, and voltages by a sometimes large amount, which I'm sure is not good for it. Through the BIOS, it's always at one clock/voltage.