Silent install apk programmatically by system app (without root)

Question

I have system-level app with android:sharedUserId=\"android.uid.system\" (UID: 1000).

Device is not rooted! INSTALL_PACKAGES permission is included to Manifest.

Answer 1

No, you cannot. Simply having the same UID isn't enough. You must also be signed with the same key as the ROM itself.

Silently installing apps, or updates to your own app, isn't allowed for security reasons.