They are not implemented!
To save your ass, PLEASE use one of package from Microsoft.Xbox.Live.SDK.WinRT.UWP.
// sign in
object dispatcher = null;
#if ENABLE_WINMD_SUPPORT
dispatcher = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
#endif
var user = new XboxLiveUser();
var result = await user.SignInSilentlyAsync(dispatcher);
if (result.Status == SignInStatus.UserInteractionRequired)
await user.SignInAsync(dispatcher);
// create xbox live context
var context = new XboxLiveContext(user);
// achievement
var result = await context.AchievementService.GetAchievementsForTitleIdAsync(
xboxUserId: context.User.XboxUserId,
titleId: context.AppConfig.TitleId,
Microsoft.Xbox.Services.Achievements.AchievementType.All,
unlockedOnly: false,
orderBy: AchievementOrderBy.Default,
skipItems: 0,
maxItems: 100 // do NOT use MaxValue!
);
use VS2015 to build your UWP project


create and put a XboxServices.config into your UWA project
{
"PublisherId": "CN=XXXXXXXXX",
"PublisherDisplayName": "XXXX",
"PackageIdentityName": "XXXX",
"DisplayName": "XXXX",
"AppId": "XXXX",
"ProductFamilyName": "XXXX",
"PrimaryServiceConfigId": "00000000-0000-0000-0000-0000XXXXXX",
"TitleId": XXXXXX,
"Sandbox": "XXXXX"
}


associate your project to the correct store app and create cert


in order to connect script debugger, you also have to give private network privilege in capabilities of appxmanifest
