I found the answer and solution:
- As for access the
adb shell
, I need to enable "Root access" for ADB in "Developer options" (this apply for stock Android 4.0.4 by Cyanogenmod but the same option could be present somewhere else in your phone) - As for File Expert, the "Root Explorer" functionality is
only available in their paid version
- I'm going to use ES File Explorer and the likes
- I haven't found a solution for access through ADT's Device Manager yet but I'm happy having 2 options above