No, the menus are different and its somewhat annoying that they don't post them.
The key differences are:
CO 84: full BF service
CO 90: appetizer and salad combined, cheese plate instead of cart.

CO85: Full BF Service, midflight snack - little chicken sandwiches and a peach/pear tart, and then cookies later, followed by a roastbeef+ cheese sandwich.
CO91: appetizer and salad combined, cheese plate instead of cart. Breakfast pre-arrival.