I have a round-corner box whose bottom I want to be flat, with 90˚ corners; the top corners I need to remain round.
using Object>Convert Point, only one of the selected points actually changes from rounded to 90˚ corner. Any suggestions on how to get the other one to comply, too?
That would be live corners?
I don't think you can use the Convert Point tool in this situation. You can set different corner options for each corner in the Object > Corner Effects... dialog, or use the Selection tool and hold down the Shift key while dragging one of the yellow diamonds at a corner to adjust them individually.