Cannot continue unless data is selected on a page

You can make the “Next” button at the end of the page disabled until all the conditions are met.

Having a button ‘disabled’ requires a workaround as well, where you create two buttons (one enabled with the “next page” action, and one disabled without any actions), and add visibility filters to each. You can find more here: Creating the Follow Function in Adalo (Followers and Following Others)