A: I don’t feel like it should be an issue.
A: The steel parts are either plated or galvanized, so you have some protection against rust. If this is used in an interior application, you should be good for a long time. I would not suggest using this in an exterior application, though.
A: The studs don't come connected to the frame. You have to screw them into place. I would recommend placing them 16 on center.
A: The spacing will vary depending on the width of your door. One stud pair is set at the front of the opening, and the other is set halfway into the pocket.
A: They are adjustable. You attach them to the floor and the top rail. All the needed screws were supplied.
A: The only thing you would be cutting (to accommodate your height) are the metal studs, and the door. The top frame (how the door is held on) should not be disturbed. The trim will also be cut to size, but that is after the door is installed.
A: If you cut off the bottom of the uprights, you’ll still be able to slide the floor plate into the bottom of the uprights just fine. No “mending” needed.
A: Generally, we say you must construct an entirely new rough opening, but I do know some people have left the drywall up on one side. There would have to be some drywall touch up in a situation like that, though. You would have to do so at your own risk. We don't have any suggestions on how best to do this.
A: Yes, one of my pock door installations had partial access to the wall. Only from one side and it was a breeze. I did have access to the full length of the header from one side.