Hi John, thank you for your reply
A)I already check the above
link that is really complete but it's more related to the certification phase, my question is more operational related.
I also checked
Airbus getting to grips with aircraft performance but it takes the info from the one above, so nothing new.
I google it but nothing emerged.
B)I'm interested in EASA requirements for CS25 twin turboprops
C) On the material I found is stated that in planning phase you have to use the net ceiling for en-route obstacle separation, we all agree, the doubt is about in flight replanning like a route change or a direct to.