Q: my iPhone 6 plus screen is flickering and the phone gets stuck. I tried restoring the phone and even updated it from iCloud. the problem still persists. This only started after i downloaded iOS 9.3.1

Hi Sanjay Anthony Singh,

Thank you for using the Apple Support Communities! I'm sorry to hear that you are having these issues with your iPhone. If you are having multiple issues with your iPhone after a recent iOS update, you may want to make sure you have a current backup of your data, then try reinstalling a fresh copy of iOS as outlined in the following article (the article is aimed at a slightly different issue, but the steps are applicable here as well):

Put your device in recovery mode and set it up again

1. Connect your device to your computer and open iTunes. If you don't have a computer, borrow one from a friend or go to an Apple Retail Store or Apple Authorized Service Provider for help.
2. While your device is connected, force restart it: Press and hold both the Sleep/Wake and Home button for at least 10 seconds, and don't release when you see the Apple logo. Keep holding until you see the recovery mode screen.
   
3. When you see the option to Restore or Update, choose Update. iTunes will try to reinstall iOS without erasing your data. Wait while iTunes downloads the software for your device.
   If the download takes more than 15 minutes and your device exits recovery mode, you'll need to repeat these steps and choose Restore instead of Update when you get back to this step.
   
4. After the Update or Restore completes, set up your device. If you previously backed up your device with iTunes or iCloud and had to restore your device in step 3, you might be able to restore from your backup during setup.

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

Regards