For 1, I think we are getting farther away from this.
Siri's current architecture now provides context into the prompt, such as the app/window that has focus and the content loaded into it. In that sense, Siri is more like the MacOS menu bar than an app. A consolidated view of Siri history may look disjointed, in that there is a lot of context hidden if all it shows is a query like "when was this building built?".
Even more so, it might not provide the functionality desired if you go look at historic chats and ask "who was the architect?", unless all that context was actually captured. However, that context was never formatted in a way that was intended to be clearly displayed to the user. That in itself creates a lot of challenges around things like user consent since Siri can farm off queries to other (online) tools and world-knowledge AI services.
There is at least a UX paradigm for this - clipboard history. Coincidentally, Tahoe built clipboard history into Spotlight. But clipboard history lends itself to perhaps being more a complete and self contained snapshot. I'm not sure Siri is being built to work this way because of implicit context.
For 2, at a certain point this gets farmed off to other tools or other AI services. The Gemini agreement is for the foundational model, not large "world knowledge" models or backing databases. Today, Siri answers this question by providing bibliographical information inline from Wikipedia, using internal tools. The model itself just isn't able to answer the actual question (e.g. it will just say his birthday).
For 3, the model already has substantial personal context (as much as apps are willing to give it) and does have state in between requests. This is actually one of the issues with Siri today - that context changes the behavior of the command and control engine in interesting ways, phone to phone and sometimes moment to moment.
Unfortunately, I think stopping and asking for clarification is not something generative AI currently excels at.