AndroidManifest.XML Question

This has been giving me headaches for about a day now, and I still have yet to figure this all out.

Some background: I got to the point where I wanted to start testing my game on my mobile devices, and originally ran into the headache of the AndroidManifest early on. On post recommended taking the AndroidManifest from Unity and modifying that to run. Low and behold it works.

Well, now I'm at the point where I'm modifying my game and files for publishing, and I realize that I need to modify the Manifest to relate to my game. So I modify the file, the game compiles fine, but it crashes on start.

Here's the source comparison. Unity's File (modified for my game that works)

 <?xml version="1.0" encoding="utf-8"?>
 <manifest
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.unity3d.player"
     android:installLocation="preferExternal"
     android:versionCode="1"
     android:versionName="1.0">
     <supports-screens
         android:smallScreens="true"
         android:normalScreens="true"
         android:largeScreens="true"
         android:xlargeScreens="true"
         android:anyDensity="true"/>
         
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 
     <application
         android:theme="@android:style/Theme.NoTitleBar"
         android:icon="@drawable/app_icon"
         android:label="@string/app_name"
         android:isGame="true">
         <activity android:name="com.unity3d.player.UnityPlayerActivity"
                   android:label="@string/app_name">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
             <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
         </activity>
     </application>
 </manifest>

And Here is mine that I modified to be unique to my game.

 <?xml version="1.0" encoding="utf-8"?>
 <manifest
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.BMyattProductions.NumberCracker"
     android:installLocation="preferExternal"
     android:versionCode="1"
     android:versionName="1.0">
     <supports-screens
         android:smallScreens="true"
         android:normalScreens="true"
         android:largeScreens="true"
         android:xlargeScreens="true"
         android:anyDensity="true"/>
         
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 
     <application
         android:theme="@android:style/Theme.NoTitleBar"
         android:icon="@drawable/app_icon"
         android:label="@string/app_name"
         android:isGame="true">
         <activity android:name="com.BMyattProductions.NumberCracker.MainActivity"
                   android:label="@string/app_name"
                   android:screenOrientation="portrait"
                      android:configChanges="orientation|keyboardHidden">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
             <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
         </activity>
     </application>
 </manifest>
 

Could I get some help in figuring out WTH I'm doing wrong. Android Manifests in Unity are driving me insane.

After some experimenting, it seems I can't rename the activity. Why is this? I've looked for tutorials explaining the AndroidManifest; however, they're more so a list of descriptions, and doesn't really explain how to build one.