Why is my android app's behavior different according to devices? -

hello made simple android puzzle game. has 2 activity classes. first activity menu options, second main game.

after pressing start button menu options of first activity, 2nd activity appears/starts. problem if minimize game 2nd activity pressing home button, , come game, starts first activity. , if press button, 2nd activity comes back.

why first activity come front when left app during 2nd activity? have no idea why first activity comes front.

my manifest

<application     android:allowbackup="true"     android:icon="@drawable/ic_launcher"     android:label="@string/app_name"     android:theme="@style/apptheme" >     <activity         android:name=".mainactivity"         android:label="@string/app_name" >         <intent-filter>             <action android:name="android.intent.action.main" />              <category android:name="android.intent.category.launcher" />         </intent-filter>     </activity>      <activity         android:name="com.senzgames.superword.gamecore"         android:label="@string/title_activity_game"         android:screenorientation="portrait"         android:parentactivityname="com.senzgames.superword.mainactivity"  >         <meta-data             android:name="android.support.parent_activity"             android:value="com.senzgames.superword.mainactivity" />     </activity>  </application> 

another thing device sony xperia e3 android 4.2.2 test on samsung s3 works fine on samsung. starts same activity left on samsung. why acting differently on different devices? in advance.

maybe have activated "kill activities" option in development tools in sony xperia e3 ?