STUDENT ELIGIBILITY VIA PIP + WCA FOR UC

I’d really appreciate any help on this if you can. This is about a disabled 27 year old who was a university student who took an agreed two years out to recover from a horrendous assault. He intends to return to university late September 2020 to complete his degree.
In May/June 2020, in order to hopefully qualify for UC once he became a student again, he applied for PIP and nsESA ‘credits only’ (to trigger the WCA) and a few days later, also applied for UC as he had no income.
The ESA credits claim was accepted and he was put on the waiting list for the WCA. However, a few days later after the UC claim was processed, he was told his ESA claim
had been cancelled ‘as he was now receiving UC which takes precedence over ESA’. It was pointed out to DWP that ESA and UC can run independently alongside each other, however the ESA advisor dug her heels in and was adamant that the ESA claim had been cancelled and could not be reinstated, nor could we appeal that decision as he’d been transferred onto the UC WCA waiting list. Incidentally, we are still well within the month to appeal if necessary.
The main aim here is to get the WCA done as it (+PIP) are prerequisites for claiming UC as a student. Have I got the right end of the stick with the following questions?:
a) will his UC be immediately cancelled once he becomes a student because he probably won't have the WCA and PIP in place by then?
b) will the UC WCA also be cancelled immediately as its linked to UC and the DWP will see it as no longer being required if he’s not receiving UC?
c) if he could get the WCA wait transferred from UC back to ESA claim, would it remain in place until the WCA has been completed, even though he becomes a student again while waiting for it to take place?

Many thanks in advance.