In Istore when application update comes firstly it updates but than after a day it again comes in I store for update at the same date I have already updated.

I had something similar happen a few times about a month ago. Th same app kept saying it needed an update. Another symptom was that the icon was showing an update was available but when I went to the updates screen the Install button changed to the Open button before I had a chance to tap it.

I fixed it by opening the app, double tapping the home button, swiping the app up the screen and then doing a hard restart.

it did happen once more after that but the same routine fixed it again and it hasn't done it since.