Testflight doesn't really work like that - for any app not approved by Apple, you can only open it with your device if the UDID is registered in the build as a tester device.
What testflight does is take your device's UDID (when you register your device with tham ) and allow the developer to rebuild or insert your UDID into the build, and then you can install to your device.
There's still no way (with an unrooted device) to install an unapproved app without the UDID in the build - testflight just greases the path for that process.
Comments
Testflight doesn't really work like that - for any app not approved by Apple, you can only open it with your device if the UDID is registered in the build as a tester device.
What testflight does is take your device's UDID (when you register your device with tham ) and allow the developer to rebuild or insert your UDID into the build, and then you can install to your device.
There's still no way (with an unrooted device) to install an unapproved app without the UDID in the build - testflight just greases the path for that process.