Exoskeleton
No, crustaceans have exoskeletons (skeleton on the outside of the body).
Crayfish have an external skeleton and starfish have an internal skeleton relying on a water vascular system for movement.
Krill is in fact a type of crustacean. Whales are typically animals that consume large amounts of the crustacean krill.
A crab
That depends on the type of crustacean in question; it varies between species.
No, prawns is definatly not a fish it is a type crustacean like crab, lobster and shrimp.
They have a type of skeleton called a hydrostatic skeleton. This type of skeleton is a fluid filled sac which is surrounded by muscles.
An octopus or squid
Shrimp are Crustaceans, so have an exoskeleton making them invertebrates as they have no spine
internal skeleton
Internal Skeleton
a sponge skeleton