Oh that's good to know!! Where can I find out about this AAFCO? And the other day I bought Merrick's Puppy Plate, or something like that

The ingredients looked great and had the most protein I could find (28% I believe).
Another quick question, are there brands that have different flavored puppy foods? It seems most brands only have one for puppies, then different for adults. Or is it okay to feed only one as a puppy, then change it up as an adult?
Thank you all so much for your help!!