Update the stage 0 version and unwind a few of the upgrade changes (#17617)

src/SourceBuild/content/eng/bootstrap/OverrideBootstrapVersions.props

@@ -9,6 +9,7 @@
     <Msft80RC2RuntimeVersion>8.0.0-rc.2.23479.6</Msft80RC2RuntimeVersion>
     <MicrosoftNETCoreAppCrossgen2Version>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreAppCrossgen2Version>
     <MicrosoftNETCoreAppHostPackageVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreAppHostPackageVersion>
+    <MicrosoftNETCoreAppRefVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreAppRefVersion>
     <MicrosoftNETCoreAppRuntimeVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreAppRuntimeVersion>
     <MicrosoftNETILLinkTasksVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETILLinkTasksVersion>
     <MicrosoftDotNetILCompilerVersion>$(Msft80RC2RuntimeVersion)</MicrosoftDotNetILCompilerVersion>
@@ -19,5 +20,6 @@
     <MicrosoftNETCoreILAsmVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreILAsmVersion>
     <MicrosoftNETCoreILDAsmVersion>$(Msft80RC2RuntimeVersion)</MicrosoftNETCoreILDAsmVersion>
     <RuntimeNativeSystemIOPortsVersion>$(Msft80RC2RuntimeVersion)</RuntimeNativeSystemIOPortsVersion>
+    
   </PropertyGroup>
 </Project>

src/SourceBuild/content/eng/bootstrap/buildBootstrapPreviouslySB.csproj

@@ -49,6 +49,7 @@
     <ExcludedPackage Include="runtime.linux-musl-arm64.runtime.native.System.IO.Ports" />
 
     <PackageDownload Include="Microsoft.NET.ILLink.Tasks" Version="[$(MicrosoftNETILLinkTasksVersion)]" />
+    <PackageDownload Include="Microsoft.NETCore.App.Ref" Version="[$(MicrosoftNETCoreAppRefVersion)]" />
   </ItemGroup>
 
   <Target Name="GetPackagesToDownload"

src/SourceBuild/content/global.json

@@ -1,6 +1,6 @@
 {
   "tools": {
-    "dotnet": "9.0.100-alpha.1.23511.2"
+    "dotnet": "9.0.100-alpha.1.23524.3"
   },
   "msbuild-sdks": {
     "Microsoft.Build.CentralPackageVersions": "2.0.1",