mmm they are actually messing up the quartus 20.1 installation while installing quartus 20.2 in our IT department I think
Would be good if quartus report an error with the specific quartus version the qpf is expected to be
instead of just telling prime pro has to be used instead of prime pro
The error you show is not version specific. It's indicating that a project that was created in the Pro edition (or converted from a Standard edition project to a Pro edition project) cannot be opened in the Standard edition (or an older version like 13.1 that did not have a Pro edition).
EDIT: saw your last post; yes, you wouldn't be able to use Standard with a Pro project.