<style>
@media (max-width: 768px) {
  #miform { display: none; }
  #mobilelink { display: block; text-align:center; margin: 20px 0; }
}
@media (min-width: 769px) {
  #mobilelink { display: none; }
}
</style>

<iframe id="miform" 
src="https://forms.office.com/Pages/ResponsePage.aspx?id=DQSIkWdsW0yxEjajBLZtrQAAAAAAAAAAAAa__fbjkBhUQklLRzBPMUU3VlpMMTZLQ0VYV1hLTk9PMC4u&embed=true"
width="100%" height="1600" frameborder="0" style="border:none; overflow:hidden;"></iframe>

<div id="mobilelink">
  <a href="https://forms.office.com/r/xxxxxxxxxx" target="_blank" rel="noopener noreferrer"
  style="font-size:18px; background:#0078D7; color:white; padding:12px 24px; border-radius:8px; text-decoration:none;">
    Completar formulario
  </a>
</div>