No, the Duolingo course did not intend to teach it, because it is only ever used in set expressions in dialect, and Duolingo is trying to teach a mix of dialect and MSA.
But anyway, the letter ن, which corresponds to the Latin letter N, is called Nuun. Nunation is the adding of an unwritten -n sound to the case ending of a noun ("case ending" is when you add a little ending to the word to indicate the role it performs in the sentence, like whether it does the action, or the action is done to it, or it owns something, etc. etc.). Nunation occurs in some situations, like at the end of many singular nouns not defined by al-, and doesn't occur in others, like with nouns definite by al-.
As I said, it is not normally written, but if you want to express it in writing, you double the diacritic used for the vowel before it. So a nunation of an A sound, "-an," is written
, and of an I sound, "-in," is written:
The letter Y in the word "Syria" represents Greek upsilon. That letter was pronounced like German Ü in the past, which is a sound between U and I, so Arabic turned it into U and English into I. "Lebanon" comes from Hebrew, and the sound O in Hebrew often corresponds to A in Arabic.