Im afraid I wont be answering many questions considering this page since most questions that will arise from it will be answered in the next page or the one after it.
I will answer this, though: Why does Celestia look like that?
Her magical powers, and the very essence of the suns magic within her is being released from within her body, since she is now unpure. Chrysalis wants to siphon this power into her own body and force it to reside within herself.