Continuity mistake: In the scene at the beginning with the boy on the Vator being sent "below", the Smiler in the lift is shown with its head turned to its frowning face shortly before it is shown changing its expression. (00:02:23)
Continuity mistake: When Amy is floating in space outside the TARDIS, her hair is down around her shoulders in the shots of her from above, but floating around her head in the close-ups of her face. (00:03:08)
Continuity mistake: When the Doctor and Amy are sitting and watching Mandy and Amy is asking what's so important about one girl crying, the Doctor has his hands clasped just below his chin, only for them to jump in front of his mouth in the next shot. (00:08:23)
Continuity mistake: When Liz 10 backs away in pain before asking the Doctor to stop making the Star Whale's screams audible, she raises both her hands in the wide shot, but only has her left hand up in the following close-up. (00:29:31)
Continuity mistake: When the Doctor first meets Liz 10, during their conversation, her hood is pulled completely over her hair in shots facing her, but some of her hair is sticking past her hood in shots facing the Doctor.
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.