Top two: Battery box
Next ones down: Access to the engine control cables/fuel lines.
Large ones on the bottom: Access to the Precleaner and the rest of the air filtration system.
Ones next to the large ones at the bottom: Access to the scavenger fan area, brake cables, transmission control cables, transmission oil dipstick, etc, etc.
You bottom photo is upside down, but it is the right side rear area, without the stoplight. You can see the armored wire cover.
Jed