Responsive Sign-up Form using Flex

What specific areas of your project would you like help with?

1. I really appreciate some feedback on my using 'aria-attributes'. I tried my best but I'm not sure I'm going in the right way

2. I used <dialog> element to show the Success message and then applied some styles to it to make it exactly like in the design. Keeping in mind the Accessibility features, is this the best approach or should I just use a regular <div> ? (Accessibility Report telling me that <dialog> is not supported in all browsers 🤷🏼‍♂️)

3. Any suggestions to improve JS code is welcome especially functions checkValidity() and showError(). Anyway I can improve those?

4. After I submitted my solution, Accessibility Report notifying me that role="list" and role="listitem" are not necessary for <ul> and <li> respectively. Please advise!

Thanks in advance