Sorry.... I'm still struggling to understand exactly what your question is, but a BFA is 'complete' when all of it's conditions have been met. They do not deal with divorce, as in the issuing of a decree nisi, only the division of assets & finances. So if the terms of the first BFA have all been met, ie, all assets & finances have been distributed as per the terms of the agreement, then it is 'complete'... It can only ever be 'terminated' by agreement between both parties or set aside by court order IF & only if the BFA was found to not comply with legislated criteria & therefore not binding.
If the terms of the first BFA have not been met, then you can take the other party to court to basically have it's terms enforced. That ability remains for the life of the BFA.
As for the second BFA , that is a separate agreement with another party, the terms of which should have been agreed to at the time of signing & I assume would only come into affect if you separate.... Hope that helps