Answer to 4:

There are many possible customizing cds. One of them is:

A = B.
B = C D.
C = [B].
D = .

All of the customizing cds, however, show a short cut. In the 
cd above, the short cut happens with the pd of f3: We can
go directly from A to D without going through C.

Another solution would be:

A = B C.
B : C | D.
C = B.
D = .


Answer to 5:

There are several short solutions:

change "*common* Testing" to "| Testing"

or

change "*common* Testing" to "*common* [Testing]"

or

change ``Implementation = "implementation".'' to
       ``Implementation = "implementation" "testing".''
  and  ``Testing = "testing".'' to ``Testing = .''

The first solution is most ''natuaral''.