It's much easier to take a train - and you won't need ID.
Yes.
By aeroplane.Ryanair is the cheapest.
2 to 3 hours!
no
Yes
No, for domestic flights, you will need a form of photographic ID, not necessarily a passport.
A passport money for ticktes and a plane would help.
No. But they will need appropriate identification if you wish to fly.
yes
humans can't fly
To fly to Scotland, you will typically need a valid passport, visa (if required based on your nationality), and a plane ticket. Make sure to check the specific travel requirements and restrictions related to the COVID-19 pandemic in place at the time of your trip.
Your destination is irrelevant. It's your starting point that is important. Check with the airline that you intend to fly with as they all have different rules. As a general rule a passport and not a driving license would be necessary to fly into Scotland. It still depends on your starting point. If that is within Europe, you may not need a passport. As I said, check with the airline that you intend to fly with.