As its name shows Royal Canin Giant Puppy is suitable for all the Giant Dog Breeds Like Great Dane,Bull Mastiff,English Mastiff,St. Bernard,Neapolitan Mastiff etc.
Yes Maxi junior is good for 4 month German shepherd dog Breed. You can also go through the specifically for Royal Canin German Shepherd Junior also.
It depends upon the several breeds whose have the several categories/characteristics in themselves regarding on their physical shape & size, but mostly we have noticed it so intensively that the pet experts have identified them as the adult dog among all breeds of dogs after having seen their physical formations which have included in 6 months old some are considered to be 1 year as an adult dog and others are selected more than that also.
In generally, the Rottweiler breed is including in the giant breed due to its inheriting with big and potential body shape/size. Having seen their potential body shape, the animal experts have chosen them as giant breed and in providing such breed of dog with the easiest digestible along with best nutritional dog foods would more beneficial. You can feed your Rottweiler the Royal Canin Giant Starter, 4kg, Pedigree puppy Large Breed 10KG, Pedigree Puppy Dog Food Chicken Milk 3 KG pack etc.