Penumbra overall storyline and a few questions?

[Yuhaney]

Is this "mental obstacle" the end part in Black Plague where Hive mind puts you through those tests in your mind before it reveals it's true nature?

Actually, I just rechecked one thing and must say that I told one thing wrong... The end of Requiem do offer you two endings, but the other ending is not the beginning of Overture, it just means that you left the place instead of dying with Red.

Someone correct me if I got something wrong either in this or some other thing in my earlier post.