Can UIStackView support iOS 8 or 7?
UIStackView is only available in "iOS 9.0 and later".
If you need to support earlier versions of iOS, check out OAStackView, a drop-in replacement which "implements most of the features from UIStackView" and supports iOS 7+.
A few minor features haven't been finished yet. I tried it out using the UIStackView-Playground project and it works pretty well.
You could also check out MarkupKit (I'm the project's author):
https://github.com/gk-brown/MarkupKit
The LMColumnView and LMRowView classes are very similar to UIStackView but work with iOS 8. They also have a couple features that UIStackView doesn't have, such as the ability to set a background color and weight-based distribution.
See this article for more information:
https://gkbrown.wordpress.com/2015/09/29/using-uistackview-with-markupkit/