There is a puzzle before like this but the prize is bitcoin but I am not sure if they got the answers already on that riddle. Now this one, I think this could be a trick like everyone else said. This is a scheme to gain followers or attract users on their platform but the truth is they will never let someone get the prize.
It is very obvious that there is nothing in the picture and as you can see their post.
Yeah most likely that there is nothing to be found useful to get the prize. This is a lame plan for marketing. If there is a way to know PK from this they should disclose the process from that image and we can see if this is legit or they just using this for their own benefit.