Hi Konstantinos
Thanks for reaching out.
If you cannot see the administrator menu on a specific .webtest, are you please able to confirm that you are actually part of the e-group(s) which are supposed to grant access? You may find this response helpful: Websites not available in OpenShift infrastructure - #2 by cregelbr.
In regards to the modules you are being prompted to update, can you please confirm whether you are updating on the .webtest preview site, or you actual production website? Please note that changes to .webtest will not impact your production website, nor will any changes be carried over once your production website is moved to the new OpenShift cloud infrastructure. Consider the .webtest exclusively as an opportunity to see how things look on OpenShift as well as to check the Upgrade Status report to gauge what, if anything, needs updating to ensure Drupal 9 compatibility.
Are you referring to the Computed Field and Custom Meta modules?
Thanks!