Is this used in the more specialized sense of changing our clothes, or would one reserve this for a more general change?
A more general change, otherwise it would be "Εμείς αλλάζουμε τα ρούχα μας"
Is there a distinction in this construction between reflexive ("each of us changes himself only") and reciprocal ("each of us changes her fellows but not necessarily herself")?
Can you be more specific, please?
What did you type? What was Duo's error message, if any?
What exactly do you consider to be the problem and what should it have been instead?
I don't see a spelling problem in the word "ourselves".