Problem with col, help?

Question

HTML

It is necessary that when opening through a computer, all 4 columns are in a row, through a tablet - 2 columns, through a phone - 1 column.
Everything works, except for the phone version, what's the problem?

<div class="container">
  <div class="row">
    <div class="col-12 col-md-6 col-lg-2">
      Привет
    </div>

      <div class="col-12 col-md-6 col-lg-2">
        Здравствуйте
      </div>

        <div class="col-12 col-md-6 col-lg-2">
          Добрый день
        </div>

          <div class="col-12 col-md-6 col-lg-2">
            Добрый вечер
          </div>
</div>
</div>

Answer 1

<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

https://getbootstrap.com/docs/4.5/getting-started/...