Why are most of my apps not opening?

[Windows Central Question]

My phone has windows 8.1 and recently stop opening most of the apps. The few that do open don't work properly. I also can't make calls, text, or even backup my phone. When I tap on anything not working it just flashes back to the start screen. I've tried powering it off and back on several times (more apps stopped working each time). I don't have a battery to remove. Is there anything I can do to fix this other than taking it back to factory settings?

 

[Toan Le]

If even native stuffs like phone and messaging don't open, I think factory reset is the only choice left for you.