Depend on the fighting speed granted to GD. If Superman doesn't get his super speed, he's at a disadvantage. He still has his strength though, so if he gets a hold of GD, it's scrap metal. That thing wasn't all that durable when it was fighting beings at its scale. They were taking chunks out of it.
I'm not sure. It depends highly on the speed gap.
Superman can't be hurt by Gipsy Danger. Meanwhile, a single punch from Superman would slag the mech.
That said, with Superman's speed being granted to it Superman would never touch it. Though if Gipsy Danger tried to throw itself at Superman it would be more liable to destroy itself than hurt Superman.