Unlocked by beating the game.
Finishing the game will not prevent you from going back to play missed levels or getting all collectibles. So don’t worry, you can get all the achievements in one play through.
*** Spoiler - click to reveal ***Once you’ve gotten your two final Red Form upgrades you can return to the first level BSL-4 Research Ward (the game will even tell you you’re ready by changing all of the electronic signs telling survivors to return to BSL-4). Once there you can use your new powers to access blocked off areas and collect the final upgrade that’ll let you escape.
Here’s a map of the Frontier area that acts as the game hub or overworld. BSL-4 is located on the Right (you re-enter from the exit).
Additionally if you’re missing anything go to the Control Room nearby. It’ll show your progress for all of the levels (with Destroyed = 100% completion).