Note that CL is explicitly declared to not be UMDable in the FAQ. The reasoning is that having your CL for a staff is "actually using" the skill, as opposed to just "emulating" it. Like how you couldn't UMD an artificer's metamagic infusion to get the benefit of it on your wand.
On the other hand, from the PHB, it's entirely possible to UMD things like expending a turn attempt.