Hi, if I'm understanding you correctly, you can't add logic based on certain field selections custom forms. You add logic to the question as a unit, i.e. if a certain answer is selected in question A, show or skip question B. If a certain answer is selected in question C, show or skip question D (or show B again). You can't apply logic to only show certain answer options of a question. This is been asked over the years a lot, I wonder if it'll get worked into the roadmap or discussed with the product team (@jon_chen) .
In the meantime you can check out @Richard_Le_ 's workaround here.
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