When I first got into sales and went through my first few demos, I would get stressed whenever the prospect would ask me questions I didn't know.
But as I gained more confidence and knew my way around a demo, I realized something that all AEs should implant in their head.
You don't need to answer all prospect's questions on a demo.
The benefit of getting back to your prospect is that it now gives you a reason to follow up with them later on (e.g. I recommend a video follow-up or lock in a follow-up call on the calendar), and they'll accept and expect it.