1 - If you've read the introduction to the game when you first make a character, they mention that a bunch of "guardians" mysteriously came out from no where to save the world from the chaos it was in (racial wars), and then the mysterious guardians disappeared after the peace was restored. Those guardians are referred to as "Eternal Guardians", so I guess it would make sense to name the game "Eden Eternal", dunno what the Eden part refers to though. Usually names of games don't really mean a lot.
I don't think they made any references to Christianity on purpose. But you will notice a lot of pop culture references in the game.
2 - I don't really understand this question but of course Eden would have it's own fantasy world like all the other games.
3 - Sadly, yes. EE is REALLY easy, and it only gets easier over time.
4 - Alpacas are the game's basic mounts, you get one when you're 25 or 30, and it's kind of EE's unofficial mascot, lol.