Unlockables:
You have to complete the following in order to get access to the unlockables:
All purchasable parts
Complete both the Collared and ORCA story modes.
White Glint Head, Core, Arms, Legs, and Head (top) Stabilizer
Complete the Defend Line Ark mission at the end of Chapter 2 (White Glint does not have to survive).
Salineos (split missiles) and 051ANNR (assault rifle)
Complete the Defeat the White Glint mission at the end of Chapter 2.
07-Moonlight (laser blade), ASB-0710 (additional boosters shoulder piece)
Defeat Orca Rank 5.
EC-0307AB (triple back laser cannons)
Complete the Attack on Carpals mission in Chapter 3.