Solution 02: Another solution would reseting your i OS device to it’s factory settings Step 01: Check if your OSX & i Tunes is up to date using software update. Step 02: Connect your i OS device to i Tunes through your computer USB cable.Step 03: Select your device in i Tunes & under Summery pane click on Restore button for your device.
Sometimes you just don't want to buy the latest, coolest gadget; or upgrade to the latest OS.
Sometimes you're very happy with what you have, and that's completely ok.
Step 04: Now Add Wi Fi network again to your wifi settings tab & If asked enter your App Store password, Now try to update your apps from App Store.
I am 100% Assure that you will able to update your Apps & download new one with this tweak.
So I called up Apple Online Support Toll Free number what they said that this was happening because I installed new operating system via Wi Fi it may cause errors because of Wi Fi network loss or network interruptions.
They said it is best way to upgrade i OS device operating system is via i Tunes.Reset All Settings Step 02: Now tap on ‘Reset All Settings’ button it may ask for device security code or password enter that then confirm again by tapping on ‘Reset All Settings’ button prompt.Step 03: Your device will reboot with reseted settings to factory default system wide.If not, choose Enable Restrictions and enter a passcode. This all depends on your reasons for giving your child an i Device in the first place.Be sure to use a 4-digit passcode that you will remember and your kids will not guess.2. If the main intent is to listen to music and play games, or if your child is very young, you may want to restrict messaging.I did not find this documented on the Apple web site, or anywhere else on the internet.