How do you unlock the CG folder with the password Shii tells you/ the blackboard tells you?
Clearly you did not search for your answer earlier in this thread as if you did you would have found my earlier post which would explain such in detail. Basically you have to fetch the zip archive from the original Japanese developer and then in a Japanese cp932/Shift-JIS locale you have to unzip it, yielding two more embedded zip archives that are each password protected. You can proceed to unzip each of those, again needing a Japanese locale, with the appropriate passwords found in the game (you seem to have found one of those).
The Japanese locale is needed because the zip archives were created by the developer in such (with a zip tool that ignores the locale encoding, violating the zip archive specification; sadly this is fairly typical) and thus all the filenames and passwords are stored in such a format. So you need to provide the passwords as strings of cp932 encoded bytes and then you will get back files with cp932 encoded file names.
Select the link for the abbreviated quote below to see my original post on the subject including all the details and ways to get around needing a Japanese locale or even needing to download the original developer zip file, etc.
I assume you are referring to the passwords of the zip archives within VQ_omake.zip available along side the game from the original developer.
The passwords are revealed in-game at certain points in the original Japanese[...]