"The girls go again."
Translation:De meisjes gaan opnieuw.
It's correct, so you can report it next time you encounter this. Opnieuw is a more neutral translation, alweer has some surprise or annoyance included in the meaning, so with more emphasis on again.
It's correct, but we don't go out of our way to include all possible answers. It's a better investment of our time to improve meaningful parts of the course, than to focus on uncommon, somewhat old fashioned answers that are way above the level of this course.
Is this question not working properly? I have tried to answer it several times, and even literally copy and pasted the "correct" answer into the answer box. It still says it's wrong. What's happening?