Should there be some kind of postposition on "este" to make it "in the evening"?
No, este and reggel (morning) can both function as time adverbs ("in the evening" and "in the morning") without any endings.
Depart was marked wrong, but I think it is right.
Yes, "The bus departs in the evening" is fine.
Isn't "starts out" also an acceptable translation of "indul"? (It was rejected.)