iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Developers Can Now Issue Free "Promotional" Copies of iPhone Apps
As an example, Smudge Apps sent us a promotional copy of Jam: Vol 1 [App Store]. Codes can be issued for existing applications and the 50 code limit is reset for each new version of an application.
In the past, it has been difficult for developers to provide review or promotional copies, instead having to reply on Ad-hoc distributions or the issuing of gift certificates.