The fridge tends to dry the cake out, so I wouldn’t store it in the fridge longer than a day. Make sure it’s covered in a cake box or airtight cake carrier.
After the frosting is set (about an hour in the freezer), wrap it in plastic wrap to make sure no air gets to it. You can also put it in a cake box or airtight plastic cake carrier to keep it fresh.
Absolutely. Store it in the fridge in an airtight container for about a week or in the freezer for up to a month. Let it get back to room temperature and re-beat it before using.
Yes, then they’re just ready to stack later.