(re: KQ4 AGI) It used to be available for download on abandonware sites, but Sierra’s lawyers cracked down on many sites a few years ago, so it’s probably harder to find now. If you don’t have an ethical problem with downloading a game that’s essentially impossible to find anywhere else, I’d recommend poking around online (start with Google!)
I read that Sierra tech support often sent the AGI game as a replacement for customers who were having problems running the SCI version. I played KQ4 on an Apple IIGS. I don’t remember exactly what the problem was, but we had a bad disk or something that we contacted tech support about. They said they’d mail us a new copy of the game — and they did — but it was a DOS version. We contacted them again and they sent us the Apple IIGS version, didn’t ask us to return the DOS one. That game sat around at my house for YEARS… but we didn’t have a DOS machine with a 3.5″ drive so we never bothered trying it. I’m pretty sure we reformatted the disks at some point. In retrospect, I bet that was one of the rare AGI versions… if only I’d known!