I am playing a divine caster with a modest use magical device skill check. Is it possible for me to use the UMD skill to emulate the arcane casting class feature to gain the benefits of wearing a Robe of the Arch magi?
It's kindof up to your GM, because the actual text of the "Emulate a Class Feature" ability refers to "activating" items. I'm pretty sure it was the intent to allow it to work, though. You'd need to make a DC 20 check every hour to emulate a 0th level arcane spellcaster (which is sufficient to activate the robe). If it's not of the right alignment, you'd also need to make a DC 30 check every hour to avoid the negative levels.