Answer to Q12.
Always follow manufacturers' instructions about how to make up and store infant feeds. Any formula that has been made up in advance with boiled water must be refrigerated if not to be used immediately, and in any case must be used within 24 hours, or discarded. It is strongly recommended however that each feed be made up individually just prior to use.
Unfinished feeds must always be discarded and never kept for use in a later feed.