Neither "curtain" nor "drape" are plural by default in English. Normally, they come in pairs but it is not necessary that they do so.
Please be cautious of expecting that your interpretation of the language is universal and absolute.
Hmmm... I suppose that is might be a regional thing, but I would use the singular form if it was just a single 'curtain'.
And let's not forget that there was once an "Iron Curtain". So, the singular form is just as valid as the plural one, depending on where one lives.
Shouldn't the "t" of "chat" be pronounced since it's followed by a vowel ("e")?
Apparently, the answer is no: pas de liaison après un nom au singulier se terminant par une consonne muette [https://fr.wikipedia.org/wiki/Liaison_en_fran%C3%A7ais#Liaison_interdite]
Sometimes I feel we are learning Duolingo French, not French. Curtains and curtains are used interchanageably.
I thought derrière meant butt! At least whenever there is a french person in a movie it is.
It's a preposition or adverb meaning "behind," and a noun meaning "bottom/butt." (Whatever word is your favorite...) Just as in English, you can call someone's butt their "behind." It's really exactly the same as in English.
You can also refer to the backside of an object (for instance, a house) in this way.
The pronunciation of 'chat' is wrong, the 't' at the end shouldn't be pronounced