1. Can you get the skeleton key without joining Thieves Guild?

2. I thought I was to do the bidding of Clavicus Vile to get the achievement. It really should have been noted that Barbas was in charge. Can this be reversed somehow, without reverting to previous saves?

On my next play through, I was planning on dispatching both the Thieves Guild and the Dark Brotherhood, but it seems that if one wants Master Training, all but three (?) masters are members of one guild or another....AAAAARRRRRHHHH!!!!! I have so got to learn to Mod!!!!
I am currently on a 360 elite.

1. No
2.
By the way, please remember to post in the Spoiler section next time.

Btw, both of those Daedric "Artifacts" do not count towards the achievements regarding Daedric Artifacts