I want user to get the notification for the new version of the app from the store as soon as the app is approved on the store. How can I do this? Do I have any option which can help me to enable this?
Notify user of new app update.
There are several ways to it.
Here an interesting link, with reference to source code as well.
h ttps://stackoverflow.com/questions/4652847/send-update-app-to-appstore-and-notify-users
Is there any way Apple can forcefully make the user update the application or notify the user on new version release immediately (withing 12 hours) after the approval?
Apple's process relies on the user logging into the store and checking for updates, then manually applying any updates they select. There is no scheme to force them otherwise, in your example.
Happily they can't. I would not appreciate, as a user, an automatic update.
Note that Apple doesn't even do it with system updates.
But you could also test, when user launch your app, if there is a newer version and let him/her know. There are many resources available on the web explaining.