Does NEC specifically require a trench for an outdoor 220 pull? The yard where I intend to place a hot tub and pull 220 service to is a covered concrete patio. Is above ground conduit OK?

I am not sure about the code but you would be better off running solid conduit the kind that has to be glued together all the way because the flexible stuf has a tendency to wear out and separate in some arears letting debirs, dirt and Ants. Bury the conduit under the ground but ensure that the location is properly marked