The value of the radio field is the wrong thing to update. What you need to do to do this is update the fields choices. I don’t think that you can change a fields settings dynamically, well you can but during the acf/load_field, not when updating values.
The bigger issue is that also want the same radio field to allow different choices depending on the question. You can’t do this. One radio field will always have the same choices. I don’t think that there is a way to do what you’re trying to do.
