Which class is not included in the superclass $Tetrapoda$?

Which of the following statements are correct for Cyclostomata?
$I$ - They have a sucking and circular mouth without jaws.
$II$ - Their body is devoid of scales and paired fins.
$III$ - Their cranium and vertebral column are cartilaginous.
$IV$ - They have a closed type of circulatory system.
$V$ - Cyclostomes live in freshwater,but migrate to the ocean for spawning.
$VI$ - They show direct development.

Circular and sucking mouth is found in . . . . . . .

What do animals of the class Cyclostomata possess at the anterior end of their mouth?

Which animal has a circular and sucking mouth located on the anteroventral side?

The larva of $Petromyzon$ is known as