How would google know you had reflashed? Isn't setup just a matter of putting the parameters into your phone? There is no handshaking with google for setup. Does your phone even have a unique identifier they can see?
Backup should work fine, but I don't think that after account re-creation you'll be able to sync it with google Of course it will depend on the Goggle's implementation on the server side, but most probably they will consider that this new account is trying to sync it self from a "different device", so server will reject the connection.