Yup! You can help the course contributors add all those different possibilities by trying them out and then reporting them using the flag. I make it into a bit of sport with these sentences where there really are a lot of not-yet-added correct options to try to catch them all!
You are definitely very welcome to ask questions or give more information about a sentence!
It's just that only flagging them actually makes the course contributors aware of mistakes or missing correct translations (unless they happen to stumble across the sentence discussion), and I think it's also easier for them to change things straight from there, so it's certainly important to flag them. I'd say flagging is for the good of the course and the sentence discussion is more for asking questions, etc. Some people don't bother flagging or don't know that that feature exists, and that's why I mention it a lot in these kinds of discussions, certainly at the beginning of a course when there are a lot of new users around. Unless of course the commenter speficies that they did flag their response already.
When you flag a sentence you help them fix it -- which makes any comments about what else should be allowed but isn't yet outdated ;-)
The placement of "nowadays" is awkward. The sentence flows better when it begins with "nowadays". Nevertheless, both placements are correct.
In English "nowadays" can only be in the beginning or in the very end of the sentence- "Nowadays I am at home/home every evening" or "I am at home/home every evening nowadays". And, as mentioned before, "I am home" is used more often that "I am at home", so should be one of the possible answers too.