I am creating an application which changes the app icon and app name programmatically.
Assuming your question is the one in title:
Is it possible to update Android Manifest programmatically?
The answer is no, it is not possible to do that programmatically.
You can enable/disable components that are declared in your manifest, but you cannot add or remove something from there, because, as the name says, it's a manifest file, which system "reads" when it installs your app. So you are declaring your app's interface in that manifest, later on you cannot change that, unless you reinstall the app with another manifest.
Assume system provided you ability to do that. Then you'd add some permission to your manifest dynamically, whereas user hasn't approved that while he was downloading your app from Play Store.