Some nouns ending in a vowel get only -r: sko skor; fiende fiender; ko kor etc.
This is what I came here to look for. I was wondering how I would be able to tell if it was supposed to be shoe or shoes, but you cleared it up. Tack!
Yes, I think Duolingo accepts contractions by default, at least some.
Skorna translates to "The shoes", so yes, Skorna är dina would mean "The shoes are yours" (speaking to one person).
What's wrong with "sko är din" i thought din was also for singular indefinate?