I got this right, but that's because I have prior German listening experience. Correct me if I'm wrong, but does anyone else hear "Sehr ist/isst Hähnchen" in the "normal" speed of the audio? I don't think it's a mistake, I'm just calling into a discussion about how Duo's audio for languages sounds to people who are familar with them beforehand.
A cockerel is a chicken - a young male chicken. Hühnchen is a young female chicken.
Hähnchen seems to be used more commonly used when buying chicken the supermarket or reading recipes - i.e. when referring to chicken as food. Hühnchen is generally only used when referring to a chicken as an animal.
I guess in the days before industrial farming of chickens for meat and eggs, it was mostly the young males that were slaughtered to eat and the females kept alive for eggs.
If you want to say you are eating chicken, using the polite form, it would be Sie essen Hähnchen.
In this example, isst is the wrong verb form to use with Sie:
Sie essen Hähnchen = you (formal) are eating chicken, or possibly they are eating chicken
Sie isst Hähnchen = he/she/it is eating chicken
Correct, Sie essen Hähnchen also means They are eating chicken.
In written form, the formal second-person (You) pronouns are always capitalised, but all other pronouns are only capitalised when beginning a sentence. There are no other differences.
In practice, you can normally tell them apart through context. As Duolingo doesn't provide any context, it generally accepts either translation.
-chen is a German diminutive suffix. Hähn- and Huhn- I think are low German He- and She- prefixes as they are almost the same as the Scandanavian words for he and she. Hähnchen = He-chick. Huhnchen = She-chick. Das Huhn or Die Henne lays eggs. ........................... Acording to google translate hen may also be a "Die Glucke" - mother hen (The lucky clucker?, glucke - luck, lucky clucker for not being eaten yet - all very funny and easy to remember but then google refuses to translate Glucke back to hen so I dont know?)