There are two things wrong with that.
First, everything with round brackets is a function.
on(...) is and event dispatcher function defining what events (listed in bracket) this particular function shall process, the function body is in { ...} brackets.
Object() is basic function creating generic object, which is a data structure holding properties and functions (called method when attached to the object). Parameter in bracket is a data to be converted into an object, rarely used.
So you can create an object named for example "playlist" by an expression:
var playlist = new Object(); // creates empty generic object
playlist.mainhall = "hell.mp3"; // creates new property (variable) named "mainhall" storing string value of "hell.mp3"
playlist.thetower = "dark.mp3"; // creates new property (variable) named "thetower" storing string value of "dark.mp3"
...so you can utilize object storing named list (associative array).
The expression Object(_root) does not make a sense as it creates simple data structure converting _root pointer into object.
The correct way of using _root pointer is _root.focus.camera.area.char.kendra.gotoAndPlay(“a”);
However that would work only if the file timeline is a root, which is only case when file is loaded standalone.
When you want the file to work regardless of on a top of what it is loaded, don't use _root pointer, refer objects relatively:
In your file, you have a "focus" object in the main timeline. That contains "camera" object, which contains "area", which contains "char", which contains "kendra".
Also you have a "controller" object in the main timeline, which contains lot of stuff including buttons and "speed_status" object.
So when you have a button script in the "controller" object and want to call a function in the "kendra" object,
you have to use a "_parent" pointer to get a level up in the hierarchy from the "controller" object to file's main timeline (which may have a name if loaded as object atop something in a game), then use object names on the path to kendra, so it is:
_parent.focus.camera.area.char.kendra.gotoAndPlay("a"); to call gotoAndPlay("a") in the kendra object.
And to control "speed_status" object, which is in the same "controller" object as the button, you call
speed_status.gotoAndPlay("a");
That's assuming that you have your speed buttons placed in the "controller" object directly.
If you have your buttons wrapped in some object and then the object placed in the "controller", then you have to use "_parent" pointer twice - first to get from the buttom wrapper to the "controller" object and second to get from "controller" up to file's timeline:
_parent._parent.focus.camera.area.char.kendra.gotoAndPlay("a");
To control neighbor object "speed_status" you have to go one level up and then dive in and call it's function:
_parent.speed_status.gotoAndPlay("a");
That's all I can see now.