Once a diamond has been set in a platinum mounting can it be adjusted or reset in the same mounting if it is crooked? Can they use the same prongs and reposition it?
I am far from an expert, but I would think it would be possible, as long as the prongs themselves are even and all the same size. In other words, as long as it's the stone that's crooked and not the setting. Hopefully others with more experience will chime in.
Yes, but the stone may need to be removed and some of the seats recut so that they are all on the same plane. You need to take this to a competent bench person and have them look it over in person.