Q: Slide to upgrade error

Hi Shrinal Unadkat,

I understand that you recently upgraded your iPhone 6 plus to iOS 9 and you are stuck and the Slide to Upgrade part. That is something I can help you out with.

Start with using the steps outlined below. They will get you sorted out with getting passed the Slide to Upgrade part and get you back to using your iPhone. 

Start with following the steps from the article below.
https://support.apple.com/en-us/HT205239
 

Use these steps:

1. Connect your iOS device to a computer that you've previously synced with iTunes. Then make sure iTunes is open.
2. Select your device. If you don't see it listed, force restart your device by pressing and holding both the Sleep/Wake and Home button for at least 10 seconds, until you see the Apple logo. 
3. If you made an iTunes backup of your device before updating to iOS 9, restore your device from that backup. If not, you need to make a backup of your device in iTunes, then restore from that backup.

If you still see the Slide to Upgrade screen after completing the steps above:

1. Restore your device. If you don't see your device in iTunes, or your computer won't trust your device, press and hold both the Sleep/Wake and Home button for at least 10 seconds, until your device restarts and appears in iTunes. When prompted, choose Restore.
2. After the restore is complete, set up your device as new.

Have a good day