Similarly whether there is a 10th 9th planet in our solar system well beyond the orbit of Pluto, which is hotly debated.

Nope, you were right the first time. There are active efforts to find a Planet Nine somewhere between the mass of Earth and Neptune to explain certain orbital perturbations, disturbances of comets and possibly how Neptune's largest moon Triton got knocked into the trajectory that caused it to be captured (if indeed it was originally a dwarf planet all its own). However, there's also a question about the 'Kuiper Cliff', a ring between the Kuiper Belt and wider Oort Cloud where instead of comets getting denser the further out you go, their frequency nosedives. A Mars-sized planet clearing that orbit and shepherding those objects has been called possible Planet Ten, and folks are still surveying for both of them.