Most of the music is without lyrics. However, some tracks do include lyrics, but not all are in real languages. The ones that include lyrics in actual languages have lyrics sung in your chosen language for dialogue. (The main example I'm thinking of is "Birth of a Wish", which, depending on your language setting, will have the robots chant "This Cannot Continue" or "Kono Mama Ja Dame")
That is, if you chose Japanese audio, the lyrics will be in Japanese, whereas if you chose English, the lyrics will be in English.
The sole exception would be the "Weight of the World Medley" featured in the [E]nd of YoRHa ending, which features the Japanese, French, and English singers of the soundtrack together.
The rest of the music with lyrics, however, appears to be in a made-up language, similar to the dialogue in Gravity Rush. See this thread:
The composer said the language is based on old gaelic and what he believes Japanese could sound like in 1000 years.
So there is likely some root words and rules that are real.
Another thread discussing this can be seen here:
Its an invented language, same with the OST of NieR 1.
Follows the same route as shadow of the colossus. Mix of english, japanese, spanish, french etc.
Take a few languages like French, English, etc, try to imagine how they transform over centuries. Make some lyrics for a song.
There appears to be a total of three title screen backgrounds.
The default title screen looks like this:
If you
achieve ending [B] (complete the game as 9S),
then you will unlock this title screen:
However, once you achieve ending [E]
and choose to delete all save data,
your title screen will change to this one:
From what I have found online, you cannot manually change them and, going down the list, each title screen appears to replace any previous one, which means unlocking the final one will make that your title screen permanently from that point forward.
Best Answer
The name is a combination of a few things. From the official Square Enix blog:
This covers the 3C3C1D part, however the date is left a mystery. Fortunately, this mystery has been solved.
From this Steam thread:
Here is the music video for "Deserving of Life" by amazarashi.