UILabel is not auto-shrinking text to fit label size

Question

I have this strange issue, and im dealing with it for more than 8 hours now.. Depending on situation i have to calculate UILabels size dynamically,
e.g

Answer 1

This is how I get UILabel Autoshrink work (especially for height of label font fitting in 4s device from 6s Plus Storyboard) in iOS 9.2, Xcode 7.2 ...

• Number of lines is 0
• Line Breaks: Clip
• Autoshrink: Minimum Font Scale 0.25