Answer 1

Need to add link to jquery cdn inorder to use jquery in your code.

Add this script to the head of your html document

<script src="https://code.jquery.com/jquery-3.5.1.min.js" integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0=" crossorigin="anonymous"></script>