I feed the NV Medallions and just love it
. You can start puppies on it right away, so 9 mths is just fine. If you go their website, naturesvariety.com, there is a spot where you can enter your baby's weight and activity level - so you can see how many medallions per day to feed, which is helpful.
I don't alternate - I really like to just feed raw since I think it's the best food for my guys. It's great if you can alternate btween flavors of raw, though - since variety is always good for dogs.
When switching to raw, most people just do a hard switch - meaning they just switch cold turkey to raw. Some dogs may have poo issues for a couple day, some have none at all (mine had no issues at all). As far as flavors, maybe buy a couple bags - like lamb and the organic chicken (not the regular).