"tidy" has been accepted and even preferred as a translation for "siisti" in other exercises. It should also be accepted here. Reported.
Would it still be correct English if I used "who" instead of "which"?
Would agree with that
As a native American English speaker, I would frequently use "who" instead of "which" when referring to animals. I have reported it.
"The squirrels, which live in the clean park, run away." should also be accepted.
"The park" or "a park" why?!
'who' is more commonly used when it is 'animate' not necessarily human and therefore I wold use 'who' rather than 'which'. I have reported it.