As a workaround for the enabled/disabled all calendars, remember the code to check if a calendar is enabled or not? (www.rainlendar.net/cms/index.php?option=com_kunena&Itemid=42&func=view&catid=6&id=14827#14828
If you instead of isEnabled = Rainlendar_GetOption("Calendars/Calendar" .. i, "Enabled")
write NameOfTheCalendar = Rainlendar_GetOption("Calendars/Calendar" .. i, "Name")
you will have (readed from the ini file) one by one the names of all calendars.
If you want to enable all: Rainlendar_EnableCalendar(NameOfTheCalendar, 1)
If you want to disable all: Rainlendar_EnableCalendar(NameOfTheCalendar, 0)
... and after the last iteration, Rainlendar_Redraw(0) to update the changes.
For the "which shows first" thing, I think you will need to create a variable (see skin.xml file on Shadow4 skin) to set and get which is the element you are showing. (This variable doesn't get lost when you redraw, refresh or close)
So, by default, all elements are hidden. Read the variable. Show which the variable says.