Based on the clue '12 beats of a gong an airplane swooping down sign...', what is the answer?

Based on the clue '12 20 feet high to keep the barbarians at bay it r...', what is the answer? What is referred to by '12 34 56 78'? Based on the clue '12 avenues radiate from place charles de gaulle in...', what is the answer? What is associated with: 12 avenues radiate from this paris structure completed in 1835? Based on the clue '12 cup of this japanese soy bean curd contains 258...', what is the answer? Based on the clue '12 hens each lay a half dozen eggs but 2 get broke...', what is the answer? Based on the clue '12 inches of hot dog', what is the answer? What is referred to by '12 inches'?