1) Примери за валидация на форми с Bootstrap 5:
> https://mdbootstrap.com/docs/standard/forms/validation/
> https://designmodo.com/validate-forms-bootstrap/
> https://colorlib.com/wp/bootstrap-form-validation/ // изберете пример, който да разгледате
> https://colorlib.com/wp/html5-and-css3-login-forms/
> https://freefrontend.com/bootstrap-forms/