OK, this is definitely fake. Some of my observations here:
-The second solo is definitely NOT Brian's playing, nor quite his sound. It's lacking a lot of the rich sometimes screaming treble that's an integral part of his signature sound. Also, it sounds like it was played with a regular pick and not a sixpence. Brian almost NEVER uses normal guitar picks for his solos. The harmonies at the end aren't even very well developed in layering. The guitarist here is probably using a guitar with single coil pickups - probably even a Stratocaster type guitar. No evidence of even a Digitech Brian May pedal at work here either.
-The main rhythm guitars don't even match Roger's typical playing style or tone either.
-The drums sound like they were looped from the original album version and processed heavily to make it sound like they were a more rough primitive sounding drum machine loop. If you listen closely during the parts where it's just the drums only, they have a metallic sounding artifact which is very apparent all over the drum sound.
-The bass guitar is out of tone by a few cents, especially on the thinner strings. Seriously, has anyone ever heard John play a song in the studio with a bass guitar even slightly out of tune?? Also, the bass sounds like it was recorded only direct rather than his typical combo of direct and miked bass amp.
And one last thing, this "demo" is missing some of that demo quality tape hiss associated with all the other genuine Hot Space demos out there! Though it's possible they could have faked up the demo, transferred it to cassette and then back in digitally, plus some hiss reduction in an attempt to give it a "demo quality."
Ahh, I love having Sony MDR-V6 studio quality headphones for days like these ^_^