A:AnswerA third rack requires a third set rails. So if you have the rails, you should have gotten the third rack (unless a previous owner lost it). You can get a third rack from GE.
If you don't have the third set of rails, you can't use the third rack in any form.
A:AnswerI don't have the instructions in front of me, but I remember a section describing how the door adjustment can be made. Of course, that will have to be done before the DW is placed in its opening.