I have an iPhone App which is available on App Store.
Now I have made some changes in my existing App which can be tested only when an App is available on App Store.
So I want to release newer version but I want to test it first before it it available on App Store for all users
And once it is tested and if it works fine as per expectation then only I want to make it available for other user.
How can I do that?
The short answer is: NO - there is no way to make an app available on the app store that only you can download and test.
If you can specify exactly what it is that you are trying to test that only works when the app is live, we may be able to suggest a different approach.
EDIT: if you just want to test the upgrade process, you can just install the new version on top of the old one - there's no need to delete the one already on the phone. For example if you download the version from the app store, run it, and then build and install a version from Xcode, it will install on top of the app store version, and keep all the settings and documents from that version, just like if a user was upgrading.
Also read up on "wireless distribution" for adhoc apps. Using wireless distribution, you can download and install the app from a link on your phone, just as if you were doing it from the app store, except the link will only work for UDIDs that were included in the adhoc profile.