How to add a custom tag in contact form 7 and change the output in email?

In the first step, the form to display, you can keep what you have coded.

Then you can do that to generate the result in the e-mail :

add_filter("wpcf7_posted_data", function ($posted_data) {

    $result = "";


    foreach ($posted_data["tag"] as $index => $question) {

        $answer = $posted_data["ans"][$index];

        $result .= "$question : $answer\n";

    }


    $posted_data["my_questions"] = $result;

    return $posted_data;

});

And in the configuration of the e-mail, just put the tag [my_questions]