(Mostly) when you long-hold, if you release without dragging after the menu comes up, the menu will stay up and allow you to tap-navigate; if you drag first, then it drag-navigates.

Sometimes this fails, though; I'm not sure that it's a bug, I think it may just be my fault for dragging a little.

I don't know of any way to reverse the menu direction; I've only ever seen one system that supported that, and I don't remember which one that was... FVWM maybe?