AFP Permission issues after new FW update

I see 4.2.18 has been pulled now. I did not do thorough testing on the permissions issue when I upgraded my first Mac to Lion and upgraded my ReadyNAS to 4.2.18. All I did was acess my existing shares. I should have known better. I always wait for a few months before upgrading my ReadyNAS to a new code release. This time around, the temptation to upgrade all of my Macs to Lion was too much to bear, so I went ahead and upgraded all of them. My bad.

I have a question about the issue of Guest access to shares being enabled after the upgrade to 4.2.18, which is the reason why it has been pulled. I see that the "Allow guest acess" checkbox is ticked on every one of my AFP shares. It's also grayed out, so I cannot untick it. It's not a major concern to me, but I can see why this is a major security hole. So, how do I untick the "Allow guest acess" checkbox?

Additionally, I have these two questions:
1. What is "guest acess" in the first place? How is it provided by AFP? What is the mechanism behind it? How is Guest different from "everyone"?
2. What is the mechanism that "grants rename and delete privileges to non-owner of files"? How is it done using the read/write/execute permissions on the local (to ReadyNAS) file system?

I have had these questions for years now. Unfortunately, the ReadyNAS manual does not get into detail on file access permissions, and all of my appeals to the ReadyNAS team over the years to create a separate document on permissions resulted in nothing.

Thanks!