The Radionics 8112 G2 revision was released in mid-1992. One of its prominent features is that the programming of each panel is restricted to only those programmers "authorized" to access them---basically, any given vendor's panels can be accessed only through the programmers (L5100 or L5200) whose CPU has the access code of that particular vendor, so the panels were essentially proprietary for that vendor.
That's the way I understood it. The company I worked for at the time were ready to take any tech to court if he claimed to have lost his programmer, because it "contained their customer base." Basically, it was made for the dealer to prevent takeovers like what you want to do. Radionics wasn't just DIY-unfriendly, it was downright DIY-HOSTILE.
About the only way I know to use that panel would be to substitute an earlier version ( I seem to remember E1 and E2 but not sure) CPU, which would accept programming from any L5100 or L5200. Your G2 version won't. But even if you could find an earlier version CPU chip, I question the economics of restoring a Radionics panel from the early 90's instead of just buying a Honeywell/Ademco Vista-20, Vista-20Se or Vista-20P off eBay and being able to program through its Alpha keypad, and have all the peripheral parts readily available to customize the system.