This is just an educated guess, but... with regard to the shot of Anakin missing his chin mask piece...

that could be the sole remaining shot in the finished film from the first time they shot that scene... with David Prowse in the bald cap, etc. playing Anakin in the un-masking scene.

Prowse was so happy that his face (even under make-up, bald cap, etc.) would get screen time in the saga, that he blabbed the secret ending to a tabloid. Lucas was furious that Prowse broke the secrecy and re-shot the un-masking scene, this time with Sabastian Shaw.