There are five achievements in Alien: Isolation relating to not doing certain things:
Mercy or Prudence?
Completed the game without killing any humans
Just out of Reach
Contacted your team and escaped Comms without being attacked by an android
Hide. Run. Survive.
Completed "The Quarantine" without being killed by the Alien
Completed the game without dying
Mind Your Step
Navigated Reactor Maintenance without dying
For any of these can you still get them if you:
- Quit and reload before the animation completes
- Reload a checkpoint
- Reload the previous save
- Reload the mission save
- Restart from the mission?
Or is the only option to restart the entire game?