Drupal 8.x

When I update this function and add the bolded I get the error:

public function validateForm(array &$form, FormStateInterface $form_state){

Delete me please :)

I am using Theme MAYO on Drupal 8.9. Is there a chance to use MAYO on Drupal 9, is there anybody who can adapt it to Drupal 9!

Regards,

Joachim

Playing around with forms and ajax but ran into problems. When I add a form element before the ones that should be added dynamically it's stops working if the element is required.  I thought I could solve it by skipping required and validate instead but it gave the same result (and I do like to have the red star :-).

I'm to much of a rookie in Drupal 8/9 to have any clue on how to solve this so I really hope there is someone with a solution.

Im running Drupal 8.9.0.

drupal 8.9.0

currently i have menu_item_role_access 8.x-1.0 and to get ready for drupal 9 i must go to 8.x-2.0
 

I have two questions : 

1)  is there any way to upgrade without uninstalling? ( and loosing all the role access configurations i have in place now)