Thanks for your review!

1) I wanted to avoid storing terminating zeros - prefix dict does not need them and it's wasted space. My contract does not need \0 after full domain in dnsresolve, but it will still work with it. This allows for using dnsresolve from command line without hex encoding.

My code is completely separator agnostic (it can be dots, zeros, or anything). Your example will in fact work - is's still a prefix. And it will return category -1 (assuming you pass terminating zero to register - this is why I don't like this interpretation of the task; if this is indeed the desired behavior, only register.fif needs to be changed). My version is consistent between register.fif and dnsresolve: "org.ton"/"org.ton.test" and 'org\0ton\0'/'org\0\ton\0test\0' both work.

2) Yes, you are right and I am wrong (I'm sure I've seen this format somewhere, several other contracts do this). Unfortunately, I can't edit my issue.