They've made it really vague on those points actually. For example their is suppose to be a crashed Ark that wasn't a total loss that many of the remaining Indogenes are studying.
Also in the timeline before the Votans left for Earth it mentions that they successfully terraformed a planet/moon there. Pretty unrealistic if the test was on a place already habitable. Which would mean they used it to terraform a lifeless hulk into something liveable. Which begs the question why they didn't do it to other places on the way to Earth. Or why they needed Earth in the first place.
But yeah... for now (and probably the foreseeable future) we only have Earth.

