Searching around yielded little to no results to answer your questions.  However, after you provided the images of the posting, I was able to translate [this image][1] using Google's Image translator app on my phone:

[![][1]][1]

Although it's not perfect, every time it seemed to come to the conclusion that the bottom bullet basically says "No software on Side B, new software can be written."

[![No Side B][2]][2]

Due to what little is available about this, I would believe that this game is only one-sided.  

<sub>Side note: I got some interesting translations, like the red text in the above image saying "Fur Peeler" - I think the red text says "Family Computer Disk System" but the plastic on the game case blurs it somewhat in the image</sub>


**Edit:**

The eBay listing stated that it contains "Super Mario Bros 2 + Volley Ball", so this particular disk seems to have two sides, but for two different games.

[![eBay Image][3]][3]


  [1]: https://i.sstatic.net/Sq9tU.jpg
  [2]: https://i.sstatic.net/213kg.jpg
  [3]: https://i.sstatic.net/dOA8el.png