The techniques of sparkling winemaking did not originate with the Benedictine monk Dom Pérignon, nor was the first purposely sparkling wine produced in the region of Champagne. Regardless, through centuries of refinement Champagne has become the world’s leading sparkling wine and the vinous embodiment of luxury and celebration.
Jessie, I don't know that it was an official change so much as it was an acknowledgement of the Champagne region overall simply calling it Meunier. This is highlighted in Peter Liem's new book on Champagne. user2130 could offer a better explanation I'm sure!
For all intents and purposes, it's just cane sugar and wine. But, some producers will argue that the type of sugar matters; citing the use of rectified grape must instead of cane sugar.
Devan, cork-finishing is referring to the closure of the bottle during second fermentation. Some producers use plastic caps, others may use cork in order to allow some oxidation during the process.
Thomas, this is referring to base wine for Champagne. I'm also not seeing any mention of permission of white grapes in rosé Crémant de Bordeaux.