Print the Octopus bodies with no support, PLA is ideal. Material, temperature and printer variations may affect the fit and wiggle of the tentacles. Ideally they should not de-attach from the body when you remove it from the build plate. After removal the tentacles should wiggle and move loosely but not fall out of their pivots. In the gif the white Octopus fit is too tight (still playable, just not as fun), Green is perfect. You can adjust the fitment with XY compensation in the slicer.

Case best printed from PETG. Open by holding base and pressing opposing corners of the lid towards each other.  

Figure out the rules for yourself - stack against each other, build one giant tower or come up with a new strategy. The Video should make it pretty obvious.