That Chinese solution looks dodgy to me.
I have the same issue, I have downgraded to 7.1.2 - I had to reinstall everything manually though, as it would not update thro itunes. I am just happy to have got the 2G / 3G toggle back.
I have spoken to Apple but they are being moronically vague and refusing to answer direct questions.
They know that the issue is with ios8. They will jsut not admit it is a problem.
Unfortunatley I get the feeling that between them and the networks they are trying to phase out 2G.
That is fine, if 3G is as good or better in terms of network coverage! BUT IT IS NOT!!!! As thousands of users all over forums all over the internet are demonstrating.
How B@@@@Y minded can you get Apple?? Fix it! You broke it!