A: Holding the knife in your right hand, look at the open area where the knife would fold into the body. In that area there is a black, metal lever. Carefully use your thumb to push this lever towards the left side of the knife's body. This action will free the blade and allow it to be folded closed.
A: I'm not entirely positive here, but I think they're mainly for aesthetics and/or they're holed for weight reduction. The hole on the back of the blade, however, is exposed when the knife is closed and can be used with a key ring or small clip to serve as a carrier and to lock the blade shut.
A: I own this knife and I'm holding it right now. My best guess is that the notch above the slot makes the knife feel more stable when you grip it. The slot itself seems to be for one, all or none of the following reasons: weight-reduction, asthetics, or to confirm the blade is fully closed (if you can see day like it's still partially open), or a string/wire cutter since the serrated portion of the blade closes right over it. Hope that helps, wish I had a more concrete answer.