I don't think "they go and come" should be marked as incorrect, since that's the literal meaning, even though in English we usually say "come and go".
I guess you would usually have "come" before "go" in english, but would it, strictly speaking, be wrong to translate it the other way around?
"They're coming and going all day long" is more often used than "come and go" as it conveys the movement it is trying to describe .
I really like duolingo ... but I also really like learning French words and sentence structures so, when DL insists on transposing French words to conform to English usage, it detracts from that goal. At the very least, I recommend in a case like this that "It is also correct to say ..." should be included as a DL response instead of just declaring "You used the wrong word ..."
I'd like it, to be said if «the whole day» or «through the whole day» are correct answers. Thank you.
Sometimes DL wants the response according to the order of the words and sometimes in more English phraseology - it would appear!
there is nothing wrong with saying the whole day long instead!! and I agree with last comments - in english we would never say go and come - only come and go!!
often your translations are too pedantic, or too literal ie 'word for word' and unlike normal english usage