Does anyone here know which, or if any of the trac…

The 15 first songs on SoC are demos recorded between July 1978 and Sept 1980. I have not seen any definitive answer as to which of those, or if any, are taken from the 1979 demo record. Does the 1979 demo really exist? It has has been a demo circulating on the web, but if it’s real or just songs taken from SoC is another question. If it is real, then a bunch of the songs on it has to be different versions than those appearing on SoC, unless the 1979 demo is actually from 1980 or later.