А после удаления app service домен останется?
1) я так понимаю вы не сможете удалить веб апп, пока к нему линкован custom domain
2) The domain may have been accidentally deleted by the owner of the subscription. If your domain was deleted less than 7 days ago , the domain has not yet started the deletion process. Hence you can buy the same domain again on Azure portal under the same subscription (make sure to type the exact domain name in search text box). You will not be charged again for this domain. If the domain was deleted more than 7 days ago , please contact Microsoft Azure support for assistance to restore the domain