How disable / remove android activity label and label bar?

You can achieve this by setting the android:theme attribute to @android:style/Theme.NoTitleBar on your <activity> element in your AndroidManifest.xml like this:

<activity android:name=".Activity"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.NoTitleBar">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>