"Humans" should be accepted but it isn't.
Plus loài explicitly means species.
In wide sense yes, but for practice in my opinion it's better to restrict to the exact meaning.
"When did humans appear?" would be something you might read in an introduction to physical anthropology, which would be exacting enough.
Words like species and human race are not A2 level material. The words such as 'wish' and 'build' (vocab from the previous lesson) are what should be introduced at this level. Not 'species'.