Strike that and reverse it.

The rolling tier is good for moving to a higher elite level, not for requalifying. But with that said, if someone does not requalify within the calendar year and they are downgraded to a lower status, the rolling year qualification can come back into play almost immediately.

As for the OP's 3rd question, there is no '75 nights within a calendar year' requirement for Emeritus status, so it shouldn't matter how you received your Plat status. It only matters that you did receive it at some point.