The basic features should work with Lemmy and Kbin, but some of the new ones are unique to Lemmy for now, such as the error page replacement. I’ve found Kbin a little harder to work with because while it’s more flexible, it’s harder to make sure I’m avoiding unintended actions.
I don’t think there are any limitations with behaw, at least with the current features.
I tested with mobile Firefox on an older version and it did work. However since you have to jump through hoops to install the extension in the first place, I haven’t looked into it much more. If you try to install it from the store on mobile, it should say that it isn’t compatible. :)