I was trying this and it seemed i had same (live) weather when changing time. Not sure how i would go about activating historical weather.
There should be two switches when live weather is enabled. One for live and second for historical. I feel that would be better approach to this.
For B (Historical 24hr) just move the time slider.
For C (Current Live Weather any time) select Custom Weather top left and then tick the Live Weather box on the new window. Adjust the time in the same window as required. I think Preset probably works as well but select Live Wx on the right.
I believe the two needs they were trying to satisfy was current live weather anytime for VatSim etc where people want to use other real world weather reporting methods and users who could only fly in the evening but wanted to fly in daylight with the weather matching that time. I think some would prefer no limit on the historical weather but 24 hours is a good start.