Can I freeze 3 day old (refrigerated) breastmilk that has not been reheated?

It is fine to freeze and to feed baby if your fridge is at a standard temp (37-38 degrees). It can last in the fridge for up to a week. Breast milk naturally has antimicrobial properties. However, do put that milk in front of the freezer so you use it first, and perhaps mark it so that you remember when you thaw it out.

If you have kept in refrigerated then yes. But when you thaw it out you must be quick with heating, and you must purify it. Pretty simple!

Yes you can. Technically any liquid substance goes to the freezer will be frozen. the fridge will not complain!! But can you feed it to your baby after that, that is another thing you didn't ask about!

Yes. However, I would also keep it to the front so you use it before the milk that was frozen fresh.

No. Freeze it fresh.

No I would feed it to your baby