Where can I find tutorials for PAS plugin.
https://docs.plone.org/4/en/old-reference-manuals/pluggable_authentication_service/
is a good start.
But in general you need to read and debug existing code or check with existing plugins.
Currently working on PAS plugin myself....the PAS functionality is in general fragile and partly weird...it took me many hours of debugging and bug hunting for integrating PAS with CiviCRM.
I have Plone 5 but these docs are for plone 4
No difference
thank you