A. That would depend mainly on the size of the herniation. It is a small opening and only fat can get in, there may be possibly no worse case scenario (entrapped/incarcerated umbilical hernia) or it may take years for an herniation to get bigger and then to become dangerous. Eventually traumas (and anything that could increase abdominal pressure) can worsen clinical signs suddenly.
It is difficult to give you a specific answers, hopefully that could help.
Your account has been reactivated.