Need to build some JS form validation on a PHP-created page

I have a PHP-created HTML page which dynamically creates a form. The page/form is basically a ballot paper that contains from 1-20 questions based on the number of questions, the questions itself and the choices for each questions which are all output dynamically from the database. The PHP that does this is already built, and I can provide the PHP file. I am trying to validate the user's inputs onto the form based on three types of questions: (A) questions that must have only one choice selected (these are radio buttons); (B) questions that must have exactly X checkboxes ticked; Or (C) questions that must have up to X checkboxes ticked. I need someone to build the JavaScript that does this, and a PHP script that accepts the output of the form, checks it server-side that it is filled in correctly and either spits out a success page or returns the user to the form with errors displayed if it doesn't. It shouldn't be a hard piece of work - I just don't know JavaScript. I can provide the files and am happy to talk through the work already done. The PHP is all built, but I am trying to build the JavaScript to validate the form.