That widdly widdly bit at the beginning.
To a non musician I can’t conceive how you would do it.
How high up the technically difficult list is it? What’s harder?

I always thought it was a combination of hammerons and pull offs, could be wrong mind.

Also I think Alex uses masses of effects, so wouldn’t be surprised to find out it’s also running through a chorus peddle and octaver..

Must be loads on YouTube about Alex..

You can buy sheet music for all of Rush, I have volume 1 somewhere. Did learn 2112 many years ago….

Not being a Rush fan I had to go and google the song. Watching it live it is actually fairly easy for any competant guitarist. Just loads of hammer-ons with open string hits in between.