Permission is only granted to system app, in Manifest

Question

I want to add this permission to my Android manifest:

Answer 1

MODIFY_PHONE_STATE is a system-only permission. System Apps are either pre-installed into a system folder or compiled by a manufacturer using their security certificate.

Hence, if you are trying to do this you are trying to use API which are no longer supported. With Android versions 2.3+ you can monitor incoming calls, but blocking is not allowed (i think from the link you posted thats what you're trying to do).

Android issues if you need to follow: Issue 15022 and Issue 14789