I am not an examiner but I am sure that the CPL is a VFR licence only (apart from the night privileges) and that the Skills Test MUST be taken in VFR conditions. It is up to the examinee to assess the weather as part of the flight planning process and make a pre-flight go/no go decision which, if completely bonkers, i.e. less than VFR conditions, could result in a fail! This would also apply to any decision to continue a flight into less than VFR conditions, the only exemption being a SVFR clearance through a CTR, if your examiner routed you via a CTR on the Nav section, provided that the SVFR minima were also rigidly applied.
I held an IMCR before the CPL Skills Test and was told in no uncertain terms that I was NOT permitted to exercise IMCR privileges during the test.
The first phase of the Nav section is Mark 1 eyeball nav only. You can set up the Radio Nav kit for the diversion during the Nav section but you can't use it before then.
You will be tested on Radio Nav aid tracking and position fixing. Keep it as simple as possible.