Well sometimes Im stuck feeding my 6months old pair (normal and pastel) small rats and they weight just above 500g. Yes it is a bit big for them, but they eat them fine, and is not something I feed them often. The smaller small rats are perfect for them though.
The yearling ball that I have eats the bigger small rats fine. he is aproaching 700g. I think your yearling will be fine.
About the adult rats, Im not sure about those, I guess it deppends if its a male or female or if you dont mind your snake getting a "little fat." Most likely I would never feed any of my males adult rats, since I dont realy like fat snakes. If you are planning to breed a female, then thats a complete different issue that Im not sure about yet =).
Edit: I feed them every 7 days on saturdays.