After
seeding the iOS 9.3 beta 3 to registered developers for testing, Apple
has made the updates available to public testers as well. Apple has added a number of
new features in iOS 9.3, including Night
Shift mode, password protection for the Notes app, and much more. As
usual, the update is available Over the Air from settings for those who already
running iOS 9.3 beta 2. To update go to Settings–General–Software
Update.

After seeding the iOS 9.3 beta 3 to registered developers for testing, Apple has made the updates available to public testers as well
iOS 9.3 also includes the ability to
password and Touch ID protect Notes, revamped News app, new 3D Touch Quick
Actions for stock apps like Weather, Settings, Compass, Health, App Store, and
iTunes Store, ability to duplicate the Live Photo as a still image,
improvements to the Health app, Apple Music support in CarPlay and new
Classroom app, ability to manage multiple Apple ID logins for iOS devices and
more.  

Here are the devices iOS
9.3 beta 3 is compatible with:
  • iPhone 6s, iPhone 6s Plus, iPhone 6, iPhone 6 Plus, iPhone 5s, iPhone
    5c, iPhone 5,     iPhone 4S
  • iPad Air 2, iPad Air, iPad 4, iPad mini, iPad 3, iPad 2
  • iPad mini 3, Retina iPad mini (iPad mini 2), iPad mini
  • 6th & 5th generation iPod touch

If you want to enable Night Shift mode on your
Jailbroken device then here is the link that will guide through all the
process. How to enable iOS 9.3’s Night Shift mode on older iOS version