"The banks are old and short."
Translation:A bankok régiek és alacsonyak.
"a bankok régiek és alasconyak" marked almost correct. As far as I can tell, it was the lack of a full stop. I mention it as you haven't seemed to worry about punctuation of that kind before.
Maybe. I can't imagine using it, but, honestly, none of the Duo sentences seem weird to me anymore.