AJAX client-side instant validation

Do you mean something like jQuery validation of the inputs before the form is submitted? If so, no, Gravity Forms does not have that. Validation done by Gravity Forms is done every time the form is submitted. If there are validation errors, the form is redisplayed with the errors highlighted. Until all validation errors are cleared, the form cannot be successfully submitted.

You can do client side validation before the form is submitted, but it would be a customization to extend the way the form inputs are accepted. Please let us know if you need more information.