There are parts of this level that aren't required to be completed in order to reach the exit elevator.
There is a free Danger Room at the end of the level after the final battle. It doesn't require you to pay energy to access it unlike most danger rooms. It is also unique because it has you backtrack through part of the level while spawning enemies instead of having you access a new area.
This level contains notably more Lumbers and Silkwings than most other Starlight Cradle levels.
Gallery
Map of Meteor Mile III.
The path to one of the two energy doors in the level.
An area with minerals and treasure boxes.
The area for the final battle.
The free Danger Room at the end of the level. Note the lack of an Energy Door.