La tua soluzione non funziona del tutto, forse ho capito male quanto mi hai suggerito. Con questo metodo non posiziono al di fuori del conteiner la classe outside ma semplicemente rimpicciolisco gli input e posiziono il contenuto di outside di fianco ad esse ma sempre e comunque dentro al contenitore padre da cui io voglio scollegarmi. Qui il codice modificato seguendo quanto dettomi:
codice:
<!doctype html><html lang="en">  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">




    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">




    <style type="text/css">
        .outside{
   position: absolute;
   left: 100%;
}
    </style>




  </head>
  <body>
    <div class="container text-center">
      <h1>DIV FUORI CONTEINER</h1>
    </div>




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




      <form class="login">
        <div class="form-group row">
          <label class="control-label col-md-3" for="v_piva">Partita Iva:</label>
          <div class="col-md-9">
            <input type="text" class="form-control" id="v_iva" placeholder="Partita Iva" name="v_iva"  minlength="11"  maxlength="11" required pattern="[0-9]{11}">
          </div>
        </div>
        <div class="form-group row position-relative">
          <label class="control-label col-md-3" for="v_nese">Nome Esercizio:</label>
          <div class="col-md-9">
            <input type="text" class="form-control" id="v_nese" name="v_nese" placeholder="Nome Esercizio" required>
          </div>
          <div class="outside">questo contenuto deve essere fuori dal container</div>
        </div>
        <div class="form-group row">
          <label class="control-label col-md-3" for="v_ema">Email:</label>
          <div class="col-md-9">
            <input type="email" class="form-control" id="v_ema" name="v_ema" placeholder="Email" required>
          </div>
        </div>
      </form>
      
      </div>








    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
  </body>
</html>