Not necessarily. Size of time unit doesn’t explicitly mean largest to smallest. For human comprehension day first makes sense because that’s the most significant piece of data usually. Likewise for time of day the hour is the most significant piece of data.
Though for computer comprehension, absolutely yyyy/mm/dd is best hands down.
That’s correct. They put out a pretty specific guideline for risk of being affected and basically if you didn’t touch the mod during that time you’re fine.