Output Checkbox Data on Template
You get all available options with the options attribute and you can check if it is selected in the current entry with option.selected

{% for opt in entry.checkboxFieldHandle.options %}
    &lt;label&gt;
        &lt;input name="fields[checkboxFieldHandle][]" type="checkbox" value="{{ opt.value }}"&gt;
        {{ opt.label }}
        {% if opt.selected %}
            I'm selected
        {% endif %}
    &lt;/label&gt;
{% endfor %}


But to be honest I don't really understand your second part

Edit
As for your field, you can display all the selected values with

{% set selectedUserGroupIds = entry.userGroupFieldHandle %}
{% for userGroupId in selectedUserGroupIds %}
    {% set usergroup = craft.userGroups.getGroupById(userGroupId) %}
    {{ usergroup.name }}
{% endfor %}