Cover view doesn't work with epubs, though it shows a sort of preview of first page of text files.
Unlike the Sony PRS-350 and Kobo, there are no collections.
Library view lists by Title and Explorer view by actual folder/directories & files, which by default are Authors on Calibre.
Calendar is a Month view. Doesn't seem to actually support notes or reminders.
Search is a bit tricky as you move arrow keys to select letters.
No series, but you could use Calibre plugboard thing to add it to title?
Given limited sort & search you probably don't want to put even 2G of ebooks never mind the almost 8 GByte.
The two text files already there are from Gutenberg.
I don't know what "pictures" supports.
The two games are called Sokoban and Jigsaw
Sokoban: It might be indeed a version of this:
https://en.wikipedia.org/wiki/Sokoban It does work like it and has maybe 12 levels. You move the character with arrow keys to push [X] crates on to dots in a maze-like space.
Jigsaw is the classic 3 x 3 jumbled tile puzzle with a free space.