how to split the string in django template?

Split is a custom filter, don't forget to create your filter, and to load it in your HTML page. Documentation for Django 4.0: https://docs.djangoproject.com/en/4.0/howto/custom-template-tags/

<h4>Skills</h4>
{% with form.instance.skills|split:"," as skills %}
    {% for skill in skills %}
        {{ skill }}<br>
    {% endfor %}
{% endwith %}

For extract character string, use filter cut:

<a href="tel://+1{{ phone|cut:'-' }}">Phone</a>

this removes the scripts from the string.