When 1-Bromo-3-Chlorocyclobutane reacts with metallic sodium in dry ether, the Wurtz reaction occurs. The Wurtz reaction is an intramolecular coupling reaction that produces a cyclic product. In this case, the reaction involves the coupling of two molecules of 1-bromo-3-chlorocyclobutane, leading to the formation of a bicyclic product where the two original carbon atoms from the bromo and chloro positions are now bonded. The structure resulting from this coupling reaction is a bicyclo[2.2.2]octane derivative. Therefore, the correct answer is option (2).
Thus, the correct answer is option (2).