They don't say much about how well these suits can work. Are the just for protection or do they actually enable human functionality in space?

Zipper on the back? I sure hope they have a rope you can use to pull it up your back. This sounds like one of those design details that movies use as plot points.

For example, on a space station a disaster depressurizes a central capsule. A single astronaut is trapped with a suit on one end of the stations and because of a zipper at the back of the suit cannot be rescued.