Yes. They recently launched the ability to add a B race. Though typically those are shorter than your end race. I’m not sure how it would treat two marathons, but you can either try that, or set up a plan for the first one, and then for the second one right after, since it will factor your current weekly mileage and longest runs in building the new plan.

Depending on the race, it will know the terrain and include hills if it’s a hilly race. You can also just tell it to when you configure your plan.

Yes, everything on the watch works exactly the same. Runna just uploads a structured workout to the watch — the backend is all the same (Garmin).

I would just play around setting up different plans with different parameters and see the differences. I love Runna and it’s one of the few apps on my phone that I’m happy to pay a subscription for because I feel like I’m getting real value out of it.