re: if he's the only cat left: see, I was also surprised when Da Ji showed up, because it did seem like he was the only one? And then he wasn't? So I'm just gonna assume that the cats don't keep great track of each other, and if Da Qing hasn't seen another one in a while, he just assumes they don't exist? IDK. But I can't help but assume that if Da Ji exists, so do others. Maybe Da Qing has just gotten fed up with all of them and is like "I am the only Cat Yashou left." "No you're not!" "Sometimes I can still hear their voices."

...and apparently I lost the language question in edits, oops. I did wonder if that loss was just around now or if his knowledge has come and gone. Plus, if the cat language itself has changed but Da Qing isn't keeping up with it, thus leading to them not being able to talk to them.