Arrange cards left and right using BS4, no parent columns

Using Bootstrap 4 and without Javascript, how can I create a layout like this when the viewport is large:   

And such a situation when the viewport is limited:   

The only way I could have looked like a large viewport layout was as follows:

<div class="row justify-content-center">

  <div class="col-8 column-1">

    <form class="card text-center" action="runthis" method="GET">
      <div class="card-header">Hello</div>
      <div class="card-block">
        <input type="text" class="form-control input-lg" name="full_name" placeholder="Full Name" autofocus="" />
        <input type="text" class="form-control input-lg" name="full_name2" placeholder="Full Name/>
        <input type=" text " class="form-control input-lg " name="full_name3 " placeholder="Name " />
        <button name="Submit " value"submit " class="btn btn-primary ">Submit</button>
      </div>
    </form>

  </div> <!-- end column-1 -->

  <div class="col-4 column-2">
    <div class="card p-3">
      <blockquote class="card-block card-blockquote">
        <h4 class="card-title ">Card title</h4>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>
      </blockquote>
    </div>
    <div class="card">
      <div class="card-block ">
        <h4 class="card-title ">Card title 2</h4>
        <p class="card-text ">This card has supporting text below as a natural lead-in to additional content.</p>
        <p class="card-text "><small class="text-muted ">Last updated 3 mins ago</small></p>
      </div>
    </div>
  </div>
</div>

      

        
        
        
      

    

This code can be seen at https://codepen.io/anon/pen/ZKoPWx

As you can see from the above code, it does not allow anti-aliasing when desired when the viewport is limited due to the parent columns of the left and right sections.

How can I do this without parent columns?