Question

Does octopus has beak it has why it is not considered as bird

Answer 1

Octopuses and squids have hard beaks. These are excellent for killing, and tearing pieces of flesh from their prey. However these beaks are entirely different from that of beaks of birds. The beaks of octopuses are made of calcium carbonate, while that of birds are made from keratin.
Also,all other defining characters of birds like wings, skeletal structure, mode of reproduction are completely different in octopuses and squids. So they cannot be considered as birds.