Does Kyros have two legs on this picture? Is that me or Kyros has his second leg back when sleeping on the first page of chapter 794?
As mentioned by Aditya, there seems to be different versions. The official US release, like several online pages, shows Kyros with only one leg:



However, Viz released volume 79 on August 2, 2016, over a year after chapter 794 was first released. A possible mistake could have very well been noticed and corrected in the meantime.

I found a scan of the original Tankōbon 79, released on October 3, 2015 in Japan. It also shows the correct picture:



Not as likely anymore but given the large popularity of One Piece, eleven weeks might have been sufficient for a correction.

So I went even further back, up to the very origin of this picture. I ordered Weekly Shōnen Jump #2323 and on July 18, 2015, this picture looked like that:



So it was indeed a mistake! 

I discovered a while later that One Piece Wiki lists all mistakes that have been found so far in each Tankōbon as well as the corresponding correction. The one mentioned here can also be found there.