

Steam and game publishers can always take your games away without prior notice.
Technically: Yes. Legally: Doubtful.
Publishers can choose to no longer run servers but to remove games from the accounts without compensation, would be legal trouble.
When Sony axed Concord, all buyers got a full refund for a reason and that reason isn’t that Sony is such a caring company.
The legal justification is right there in the byline of the article you’ve linked.