It differs by market so far as I have seen. Important always to check the fare class for the fare family - it doesn't always map as you have described, and to also check the conditions.

And the range of fare 'families' changes as fares are uploaded and changed for the various promos and season.....

I once had a J fare that would not allow any changes until after the first segment was flown, and then at a fee. It was cheaper to cancel and rebook than go through such nonsense!