Are you able to fuse kyurem with reshiram or zekrom?
Yes. The DNA Splicers are in the Giant Chasm once you get the Hiking Boots.
No, they are actually outside of the house where you catch Darkrai in Nightmare Badlands I believe.
No, the DNA Splicers really are in the Giant Chasm. You’re thinking of the Reveal Glass.
Oops, haven’t played to that part in a while :3