A: No, it does not come for a round box.
A: I didn't see any on the shelf but the manufacture should consider this idea.
A: This device is supposed to mark the position of outlets and switches so an accurate home can be made in the board
A: Put it inside the gang box. Set your drywall in place, and press the drywall into the pins. Remove the drywall/Handymark, and connect the dots made by the pins. Cut the hole for the outlet. Reset the drywall, and screw into place. Set your outlet covers.
A: It marks the location of the electric box on you drywall when your installing it, so that when you cut the drywall the hole is in the right place and the right size.
A: Marks the back side of the gypsum board to indicate the location of a receptacle.