2-child limit - coercive relationship - backdating of CRE

What are the rules on backdating where some CRE has been refused due to the 2-child limit, but it is later accepted that the children were conceived in a coercive/controlling relationship?

Will the CRE be backdated to when the children were born/added to the UC claim? To the date it was reported that the relationship at the time of conception was a coercive one?
Will I have to lodge an appeal to preserve backdating -  i.e. by overturning the eventual decision to refuse the additional CRE?

The issue atm is that our client’s health worker had refused to sign the NCC1 form, because she (and her superiors) thought it was too onerous…