yea demo is for stores
retail is free and you can upgrade it with a internet connection or usb thing if you put it on there
your wrong store firmware has a different signiture than retail (personal) PS3s use
Ive personally tried with the PS3 at bestbuy I unlocked it out of demo mode and pluged my usb drive into it with 2.80 loaded on my USB and it wouldnt find the update data.
Also a store PS3 is basically a normal PS3 but they have some specialness in them usually they have a 150GB HDD and they have all hardware a normal PS3 does, but they use a different signature than retail PS3s do if you download a retail PS3s firmware
2.80and download a stores firmware
2.80 if you just compare the urls I just gave you can see they are different but take it even further and open them both in a hex editor thay are completely different.