I'm interested in non-classic problems here on Codeforces, so I've looked through the problems with special tag. The ones with non-standard format are:
- Problems that can only be solved in a single special language, such as Q# or a secret language. Example: the whole Kotlin Heroes 5: ICPC Round and Unknown Language Round #1 contests.
- Problems with a stateful checker, which detects how many submissions one has made. Example: 409H - A + B Strikes Back.
I also vaguely remember a problem where one had to output his username, but it could be just a comment on a blog.
Anyway, I can't find out how to create any similar problem on Polygon. Obviously there's a whitelist of supported languages so I can't just choose, say, Brainfuck in a list. But what about adding an interpreter for the language in C as a separate file? Or allowing the checker to read the original code, not its output? I'm interested how this is implemented for the official contests and if I can do that in a gym.
As for the second type, it'd be useful if the checker could get meta-information such as the user handle or ID, and access a local DB or use network as a state store. I couldn't find any sane documentation so I'm asking here.