Generally yes, unless stated otherwise.
Basically assume that person always was that gender and had that name.
There are some edge cases with people like actors, where things like their work is footnoted with something like "credited as XYZ". although some people are feeling even that is still bad. (I don't have a skin in the game, this is just what I know from trans people around me)
Yes but Elliot page wasn't in this movie. Ellen Page was. If he makes a movie now of course it's Elliott page but I think it's weird to go back in time and erase things.
Hi, trans person here. I often describe my life before beginning to transition as an act or a job I had to perform, but wasn't really me. Anything I did in my old role was done by me, not the character.
In Elliot's case, he was a dude playing a dudette, dressed up as another dudette. Whatever performance was happening on or off camera doesn't ultimately change who the person actually is.
That's very logical and easy to understand. Personally I wouldn't be upset if I was Elliott, but there are many trans people who have a strong aversion to hearing their old name. Again, comes down to the audience, but a lot of folks would say something like, "before he transitioned", rather than mentioning the old name.
Hope I don't sound too nitpicky, just wanted to say it in case it helps.
My nitpick would be less about the mention of the name and more about the wording of "when he was". Of course different trans people will view their transition and identity differently, but I was never <deadname>. I was merely known as <deadname>