eggs
seastars, or starfish may be poisonous
bacteria
they move by the bottom of their arms
Seastars are invertebrates.
squid and seastars
seagulls, crabs, some fish, seastars
No -- starfish or seastars are echinoderms and as such are invertebrates. -- no spines.
they are in kingdom animalia but it doesn't have a backbone
Clams, oysters, and small fish, because they are carnivorous.
The seastars don't have houses they live on the coral.
Seastars are not recommended as pets for the average person as they have specific care requirements and can be challenging to keep in a home aquarium. They also have specialized feeding habits and can be delicate to changes in water conditions, which can make them difficult to care for in a home setting.
Some types of starfish eat other smaller species of starfish, if that was what you were getting at.