Protects internal organs
Supports the body
https://humanbodyanatomy.co/parts-of-the-body-anatomy/parts-of-the-body-anatomy-anterior-and-posterior-parts-of-the-body-anatomy-human-anatomy-chart/
this link has a picture with the posterior region.
Squats and lunges
Hope this helps
A sign on the road, it could be multiple colors.
The answer is Less then 5