Why can't I open messaging, email, camera, photos and contacts on my HTC 8 phone?

[Ckwe]

I can't open email, messaging, photos, contacts, camera, etc. on my HTC 8 AT&T windows phone. I tried to download 8.1, it downloaded but couldn't install so not sure if it has locked up my phone. Have removed all additional apps and photos, did several soft resets, hard factory reset and several more soft resets. I was able to access for a day and it went away again. Contacted AT&T and Windows help and was told I had to by new phone because I've had the phone 15 months.