I couldn't get the modified Face by BRepFilletAPI_MakeFillet::Modified(), so I couldn't trace the Face evolution.
I use TopExp_Exlorer to iterate all the face of shape, the use each TopoDS_Face as parameter to call Modified, but each calling return a null list. In other words, I couldn't get the modified face corresponding face before modification.
I take a look at the source code of MakeFillet, I found it delegate this task to its internal builder and call a function: IsSplit. I suspect only merging or spliting face can be recorded.
Maybe it is unnecessary to keep this information to persistent naming fillet operation. If someone could tell me how to topology name a fillet operation, I will thank him/her in advance.