"billion" in the US means 10^9, but in France, Germany, Austria, Belgium, etc means 10^12.

Trillion means 10^12 in the US but means 10^18 in the above places.

Is this true even if you're speaking English in France? I would assume in English, it always means 10^9.

Is a billion a million million, or one followed by twelve noughts (1,000,000,000,000) or is a billion a thousand million?

Same thing for a trillion. I think the first is or maybe was a UK'ism. Maybe the rest of the world does that too?