unload 2

adapters.post.js

import DS from 'ember-data';

export default DS.RESTAdapter.extend({
  host: 'https://jsonplaceholder.typicode.com'
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  actions: {
    loadPosts() {
      this.store.findAll('post');
    	this.send('refresh');
    },
   	unloadPosts() {
    	this.store.unloadAll('post');
      this.send('refresh');
    } 
  }
});

models.post.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  "userId": attr(''),
  "title":  attr(''),
  "body":  attr('')
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  i: 1,
  async model() {
  	this._super(...arguments);    
    return this.store.peekAll('post');
  },
	actions: {
  	refresh() {
			this.refresh();
		}                                
	}
});

serializers.post.js

import DS from 'ember-data';

export default DS.RESTSerializer.extend({
  i: 0,
  normalizeSingleResponse(store, primaryModelClass, payload, id, requestType) {
    payload = {
    	post: payload
    };
    
    return this._super(store, primaryModelClass, payload, id, requestType);
  },
  normalizeArrayResponse(store, primaryModelClass, payload, id, requestType) {
    let max = 2 + this.i;
    payload = {
    	posts: payload.slice(this.i, max)
    };
    this.i = this.i + 2;
    if(this.i === 8) {
    	this.i = 0;
    }
    return this._super(store, primaryModelClass, payload, id, requestType);
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}

<button {{action 'unloadPosts'}}>unload</button>
<button {{action 'loadPosts'}}>load</button>

<br>

{{#each model as |m| }} 
	title:{{m.id}} - {{m.title}} <br>
{{/each}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}