Installing Phone Doctor Plus
For knowing any problem of your phone you can download Phone Doctor Plus, This app is available for free on Google Playstore.
How to Use
When you open the app you will see there are some tabs, there are tabs( Outer Hardware, Inner Hardware, Sensors and Wireless). Clicking on tab show you some options, like: in Outer Hardware there are options like: Multitouch, Touch Screen Display, Earphone and Mic, Speaker and Mic, Headphone Jack, Camera Flash, Home Button, Power Button etc.
If you think your phone's camera or home button or any part other part is not working properly, so click on it. After touching it start's searching for any error, after compeleting the searching process it shows you the result if there is no problem the app shows you green but if there is any problem then it shows red. So by using this app you can know your phone is working properly or not.