Yes, the model number would have to be GSS25QFMC BB (with a "Q").
** Refrigerator and freezer shut down, intermittently , mimics a defrost cycle for hours, temperature in freezer goes higher than 40 degrees Fahrenheit. Even though there is no excessive frost or moisture on walls of freezer. Is this a motherboard problem ? **
Yours is one of GE's electronically control fridge models (unfortunately) and does have a "motherboard" (aka electronic control circuit board) which could possibly (or not) be the cause of your symptom. Unfortunately such a system can be difficult to diagnose. It you're lucky the circuit board will have visual signs of failure if it has failed.
Early such models did have a problem with their thermistors (electronic temperature sensors) which could cause the control to act unusually. The original ones used to be bullet shaped with a rounded tip. If that is the style of the ones on your model, I would suggest they they be replaced to the current flat-tipped replacements (see the following link).