My rotors arrived with six black torx bolts.
I used my existing stainless ones, though

The pads on the Avid brakes have a tab at the bottom that rubs on the rivets of the hope rotors when the pads are worn. This can cause issues so generally we can't recommend using the Hope rotors. People have modified their brakes to run with the Hope rotors but this is not advisable.

Should be fine.

Yes

As long as the diameter matches your existing rotor it should be fine. Floating means it has a small amount of movement on the rotor spider.

Listed by the add to basket options.

We can't recommend that you do this as we can't predict if there will be any contact between the rotor and your brake caliper in use. You should contact Avid to be sure but be aware that it will likely void the warranty on your brakes if you do so.

I beleive there is a issue with the rivets catching on some brake calipers so I can't recommend that you use this Rotor on Shimano brakes.

The thickness of the rotor braking section stays the same regardless of size (2mm)

Yes these rotors are suitable for Hope mini X2 brakes.