It is said that "Assassin" (if it excists at all!) is a demo that is similar to Innuendo.
Similar to Innuendo doesn't mean it's a demo to Innuendo. Seaside Rendezvous is also similar to Lazing On a Sunday Afternoon. And Love Token is similar to Fat Bottomed Girls.
I doubtr that Assassin excists, and if it excists I seriously doubt it is similar to Innuendo. For all we know the 'demo'(?) starts with a drumroll or something.
There have been made many many many mistakes this way. For example someone heard Roger play a simple drum pattern in the soundcheck in Paris 2005 and posted on the internet that the band played One Vision in the soundcheck. While it was just Roger playing a simple drumpattern
"On the first day Pim & Niek created a heavenly occupation. Pim & Niek blessed it and named it 'Loosch'."