No, was build after Titanic, but are the same size.
No, although it was built at the same shipyard, I believe.
Queen Mary is younger than the Titanic and also a bit larger. It is built from the same company but it is not a sister ship of the Titanic. Titanic itself has only two sister ships: Olympic and Britanic
It's actually much more powerful than Titanic.
Thanks! Your answer is awaiting moderation.