Convert an iOS 8 compatible app to iOS 9

When iOS 8 came out, I had to change my iOS 7 app to be compatible with iOS 8 on code side (using objective C) and especially on UI side, like changes to search view controller and enhancements for iPhone 6 Plus.

So as title indicates; I want to convert the iOS 8 compatible app to iOS 9, what is the best approach to do so? What are the changes in iOS 9 that are not obviously shown or tricks faced in UI mainly?

P.S: I am using Xcode 7 beta 4 right now, and am seeing errors that were passed by Xcode 6. P.P.S: Please Take in consideration that this is a universal app, for iPhone5s and later and iPad 4 and later.