1. Never reheat rice unless you have a vacuum sealer and use it while rice is hot.
2. Depends how quickly you cool and put away, and how you store it, but use your eyes and nose. Except for pork products (2-3 days), most things will be OK for a week, although with cooked green items their flavour tends to go quite quickly.
3. Never store opened tins, especially with any tomato or fruit content, as this will "eat" the tin