Working AF2 plunker

<!DOCTYPE html>
<html>
  <head>
    <title>Angularfire2 Example</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- 1. Load libraries -->
     <!-- Polyfill(s) for older browsers -->
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>

    <script src="https://unpkg.com/zone.js@0.6.23?main=browser"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3"></script>
    <script src="https://unpkg.com/systemjs@0.19.27/dist/system.src.js"></script>

    <!-- 2. Configure SystemJS -->
    <script src="systemjs.config.js"></script>
    <script>
      System.import('app').catch(function(err){ console.error(err); });
    </script>
  </head>

  <!-- 3. Display the application -->
  <body>
    <my-app>Loading...</my-app>
  </body>
</html>


<!-- 
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
-->

import { Component } from '@angular/core';
import { AngularFire } from 'angularfire2';
import { Subject } from 'rxjs/Subject';

@Component({
  selector: 'my-app',
  template: '<h1>Angularfire2 example app</h1>{{res|json}}'
})
export class AppComponent {
  
  private limit: Subject<number> = new Subject<number>();
  res: any;

  constructor(af: AngularFire) {
    af.database.list(`test`, {
      query: {
        limitToFirst: this.limit
      }
    }).subscribe((val) => {
      console.log(val)
      this.res = val
    });

    this.limit.next(1);

    setTimeout(() => {
      this.limit.next(2);
    }, 2000);

    setTimeout(() => {
      this.limit.next(3);
    }, 4000);

    let random = Math.floor(Math.random() * 10);
    setTimeout(() => {
      af.database.object(`test/i0`).set(random);
    }, 6000);
  }
  
}


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AngularFireModule } from 'angularfire2';
import { AppComponent }   from './app.component';

@NgModule({
  imports:      [ 
    BrowserModule,
    AngularFireModule.initializeApp({
      apiKey: "AIzaSyDFbuKX0UeXje-PRAvwIymYo2jk-uGqMa4",
      authDomain: "test-bc800.firebaseapp.com",
      databaseURL: "https://test-bc800.firebaseio.com",
      storageBucket: ""
    }),
  ],
  declarations: [ AppComponent ],
  bootstrap:    [ AppComponent ]
})

export class AppModule { }


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app.module';

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

/**
 * PLUNKER VERSION
 * (based on systemjs.config.js in angular.io)
 * System configuration for Angular 2 samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    // DEMO ONLY! REAL CODE SHOULD NOT TRANSPILE IN THE BROWSER
    transpiler: 'ts',
    typescriptOptions: {
      tsconfig: true
    },
    meta: {
      'typescript': {
        "exports": "ts"
      }
    },
    paths: {
      // paths serve as alias
      'npm:': 'https://unpkg.com/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      app: 'app',

      // angular bundles
      '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
      '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
      '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
      '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
      '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',
      '@angular/upgrade': 'npm:@angular/upgrade/bundles/upgrade.umd.js',

      // other libraries
      'rxjs':                       'npm:rxjs',
      'angular2-in-memory-web-api': 'npm:angular2-in-memory-web-api',
      'ts':                         'npm:plugin-typescript@4.0.10/lib/plugin.js',
      'typescript':                 'npm:typescript@2.0.2/lib/typescript.js',
      'angularfire2':               'https://npmcdn.com/angularfire2/',
      'firebase':                   'https://npmcdn.com/firebase@3.4.0/',
    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.ts',
        defaultExtension: 'ts'
      },
      rxjs: {
        defaultExtension: 'js'
      },
      'angular2-in-memory-web-api': {
        main: './index.js',
        defaultExtension: 'js'
      },
      angularfire2: {
        main: 'angularfire2.js'
      },
      firebase: {
        main: 'firebase.js'
      }
    }
  });
})(this);


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}