Increase RAM allowance for Windows Phone 8.1 - windows-phone-8.1

Question

To which file am I supposed to write information that my WP8.1 application requires 300+ MB RAM? I would like to use this setup at least for the time of developing app, later I will consider other approach, targeting all devices.
As far as I can see I have only one manifest file in my project, Package.appxmanifest, shown here. I wrote the line "m3:MinDeviceMemory"1GB"/m3:MinDeviceMemory" but it doesn't seem to be enough. I have no idea where to write ID_REQ_MEMORY_300 as recommended in msdn here.
https://msdn.microsoft.com/en-us/library/windows/apps/jj681682(v=vs.105).aspx
I see no "App" object in any of my files so I can't write any "Requirements" or "FunctionalCapability" object too. Where can I find it?
<?xml version="1.0" encoding="utf-8"?>
<Package xmlns="http://schemas.microsoft.com/appx/2010/manifest"xmlns:m2="http://schemas.microsoft.com/appx/2013/manifest" xmlns:m3="http://schemas.microsoft.com/appx/2014/manifest" xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest">
<Identity Name="1cd9812c-28c9-4bc9-b45b-933beb09ad48" Publisher="CN=Štěpán" Version="1.0.0.0" />
<mp:PhoneIdentity PhoneProductId="1cd9812c-28c9-4bc9-b45b-933beb09ad48" PhonePublisherId="00000000-0000-0000-0000-000000000000" />
<Properties>
<DisplayName>Chess Openings</DisplayName>
<PublisherDisplayName>Štěpán</PublisherDisplayName>
<Logo>Assets\StoreLogo.png</Logo>
</Properties>
<Prerequisites>
<OSMinVersion>6.3.1</OSMinVersion>
<OSMaxVersionTested>6.3.1</OSMaxVersionTested>
<m3:MinDeviceMemory>1GB</m3:MinDeviceMemory>
</Prerequisites>
<Resources>
<Resource Language="x-generate" />
</Resources>
<Applications>
<Application Id="App" Executable="$targetnametoken$.exe" EntryPoint="Chess_Openings.App">
<m3:VisualElements DisplayName="Chess Openings" Square150x150Logo="Assets\Logo.png" Square44x44Logo="Assets\SmallLogo.png" Description="Chess Openings" ForegroundText="light" BackgroundColor="transparent">
<m3:DefaultTile Wide310x150Logo="Assets\WideLogo.png" Square71x71Logo="Assets\Square71x71Logo.png">
</m3:DefaultTile>
<m3:SplashScreen Image="Assets\SplashScreen.png" />
<m3:InitialRotationPreference>
<m3:Rotation Preference="portrait" />
</m3:InitialRotationPreference>
</m3:VisualElements>
</Application>
</Applications>
<Capabilities>
<Capability Name="internetClientServer" />
</Capabilities>
</Package>

Answer 1

All this my question is wrong. There is no ID_FUNCCAP_EXTEND_MEM any more in Windows Phone 8.1 compared to Windows Phone 8. This is what I was looking for all the time.
There is no default and extended memory limit in WP8.1 but just one default memory limit and it is the high one. After checking
Windows.System.MemoryManager.AppMemoryUsageLimit
I quickly recognized that my program wasn't failing because of insufficient memory, as I thought.
I guess
<m3:MinDeviceMemory>1GB</m3:MinDeviceMemory>
(as shown in code) can limit lower memory devices from store, but this isn't what I was looking for.