Yes, an article is always necessary before a proper noun in modern Greek. It can be either an indefinite or a definite article. But please pay attention to their difference:
- Η Ελένη πίνει γάλα. (= Helen is drinking milk.) --> You know Helen. (definite article)
- Μία Ελένη είναι στο τηλέφωνο. (= A Helen is on the phone.) --> You don't know who is on the phone, you just know her name. (indefinite article)
I hope that this helps. :-)
It's a [ɣ] sound, to use the IPA symbol -- a voiced velar fricative.
The sound doesn't exist in English, so it's hard to describe it well.
If you know Arabic, I believe that ghayn غ sounds the same or similar.
It's the voiced version of the letter χ before a back vowel (that one is [x], a voiceless velar fricative).
It's pronounced at the same position in the mouth as "g" as in "golf" but it's not a stop/plosive (where the tongue completely blocks the flow of air and then suddenly releases it) but instead a fricative (where the air can flow continuously but there is turbulence at that position). You can say γγγγγγγ... continuously.
You describe it very well (your comments are always very clear and helpful anyway. Thank you from a true beginner in Greek.)! So we just have to say "g" (go) and "k" (kayak) without blocking the air flow to get the [γ] and the [x] sounds. I would add it's different before the [ε] and [i] sounds: γ is then pronounced like "y" (you) and κ like "ch" ( in German ich). I think you would have more talent than me to describe these last 2 sounds in more rigorous phonetics terms.
Some contractions are generated automatically, e.g. for "I'm" from "I am", but I believe this is limited to pronouns.
So contractions after nouns would have to be entered manually. I can add "Helen's" as an alternative for "Helen is" for this sentence, but we can't go through all the thousands of sentences and add contractions to all possible combinations of noun + verb.
So you may be better off not using contractions when you type your answers, as an uncontracted sentence is more likely to be accepted.