I wonder if they are sure that similar exercises weren’t in the learning set for AI. Such competitions have usually kind of patterns for exercises and people usually learn to them by resolving a large number of exercises to catch the pattern.

I'm using http://deb.debian.org/debian mirror, but I was surprised that it didn't download files with apt-get update command. I removed /var/lib/apt/lists directory, and it worked and upgraded to 12.1 :).

I've upgraded packages several times. My base-files package has version 12.4. I've tried with apt update and apt upgrade -s and I don't have any package to upgrade. Is it possible that the version is locked somewhere?