If you mount in the floor it would but if you are locating it at the bottom of the stairs it will move air into the room at the top of the stairs. This fan is very powerful at the lowest speed but it is very loud!
Yeah, the tube frame is what mounts to the wall so you should still be able to pose it once mounted. Its more of an up/down adjustment, and you wouldn't be bale to move it left or right once mounted because of how the frame is. Just be sure to tighten the bolts that fasten the blade to the frame so that it is tight enough to hold it in place but loose enough that the fan itself can still be moved.