Not sure how you'd effectively protect UF above ground, but sure. If your going to run conduit might as well pull individual wires.
A sleeve of conduit where it leaves the dirt, just like with MHF.
OP: I am going to assume that whatever reason kept you from going underground from the meter to the garage will be the same reason you can't go underground from there to the mini split, but depending on where the mini split is in relation to the meter, how about conduit really low on the wall? If they are on opposite sides, that isn't a very good option though and the best bet would be to go ahead and add a sub panel off of the 200 amp panel in the house.
