Hey,
I updated my OS with ios 9 beta. Since this, I cant's compile my app from xcode 6 because my phone is ineligible. And if I use Xcode 7, I must compile with swift 2.0
How compile ios 8 app for iphone ios 9
Ad hoc distribution is the supported mechanism to use if you want to build using an old version of Xcode and load the application onto a device too new for that version of Xcode.
There are hackish work arounds involving swapping between Xcode 6 and Xcode 7, but that's likely to cause handshaking problems with the device.