Claiming ESA assessment rate after WCA & MR failed

Hi
If found “Fit for Work” at ESA re-assessment and this decision is not changed at MR, I understand the ESA assessment rate can be claimed from the date an Appeal is accepted by the Tribunal Service until the date of the appeal hearing.
I understand this is the case provided it was the first time a “Fit for Work” decision has been made and provided Universal Credit was not claimed in the period between being found “Fit for Work” and lodging the appeal (i.e. claiming nothing apart from “nil income HB” during this period).

My questions (given the above):
1. Would ESA assessment rate payments be BACKDATED to the date of the (failed) WCA decision?

2. If the claimant LATER decides to withdraw his appeal (due to feeling too stressed at the prospect of attending the Tribunal hearing), would he then need to pay back to DWP the ESA assessment rate payments received?
I.E. Would the ESA assessment-rate payments received from the date Appeal was accepted to the date appeal was withdrawn be owed back to DWP?

A family member may consider lending money during the period of nil income from “Fit for Work” WCA re-assessment decision until Appeal is accepted, but that would depend on the answer to qu. 1.

Qu. 2 is important to ascertain whether claimant would accrue significant debt to DWP if he LATER decides he’s unable to attend Appeal Hearing due to stress involved (& exacerbation of severe mental health issues result in withdrawing his Appeal).

I help care for the claimant who has learning difficulties, in addition to mental health illnesses. He is illiterate and hence the reason for me subscribing to this website and asking questions on his behalf.
Thank you for any responses/ thoughts you can give to my 2 questions.