I'm trying to understand the layout of our Default incident template

When I edit the template I can see the following fields above the Description box:

However, if I log a ticket I see some additional fields that are not in this template (this is the section marked "Request Details")

I assume this is because fields like "Department" depend on which Requester is selected when you log the ticket

In any case, there is also a "Requester Details" section below this, which also contains Department.

What I want to know is :

a) The 'Department' in "Request Details" and "Requester Details" - are they the same information?

b) If so, that means its possible to display Requester details in the "Request details" section.  Is it also possible to add custom Requester details to this section?  As above I've created "AP Test field" in the Requester Details, but would like to know if its possible to move to the section above (particularly, below the "Site" field).  As it's not displayed at all when I edit the Default template, I'm not sure whether it is.

c) Finally, is it possible to rename any of the standard fields?  Again, I'm thinking of renaming Site, but need to know if its a possibility.