could not activate iphone

Let's see, you have an unauthorized copy of Apple software that you are not supposed to have on your iPhone, it is beta software so it is know to have issues, it is available for people to test and report these issues but since you aren't a developer and don't have access to the developers forum you can't report these issues and you can't activate because you can't enter your UDID number as you don't legitmately have this software on your phone. And heaven knows where you got it from.

And you want to blame Apple for this? Look in the mirror and you will find out who is at fault for this situation.

In the meantime, put your iPhone in DFU mode (Google it if you don't know how) and Restore it from your backup on your computer and you will be able to use it. In the state it is in now you may not be able to update to the released version.

It is not wise to use a production device to test beta software.

I actually called Apple Developer Support and they suggested me to open the iphone in recovery mode to restore (it will delete all the data in it). Refer to article HT1808. It should solve the problem.