I have it on very good authority that the scrapped set which included Back That Up, Candy Shop, 4 Minutes and Music was intended to follow DCFMA and was designed to be a dance off battle between M and the dancers.
The whole act was scrapped after M got sick, she didn't have enough strength to perform this set as it was very dance-heavy.
Frozen was scrapped right before Manchester, M apparently thought it felt too dark and depressive so she switched it to Rain which has more of an uplifting vibe. Apparently, you can still here a note of Frozen right after Ray of Light ends and before Rain begins.
