There are mimed performances of "Liar" on the video "Rare Live", one presumably on their rehearsal stage, and the other in a very bright TV-studio kinda atmosphere. Nothing special, and annoyingly credited as "live performances" on that DoRo-mishmash.
For "Keep yourself alive" the BBC cut together apparently randomly old footage from their archives - looks very strange. Snippets can be seen on Magic Years.
As for KYA on the DVD GVH1, I don't remember, have to watch it again, but I think it is a performance, isn't it, fellow QZers ?
Guten Tag und Guten Abend !!! We had a great time in Cologne. Drinking beer in the sunshine beside the Mighty Rhein brought back many memories for me..... (Brian May, 2004)