The thyroid gland is homologous to which part of lower vertebrates?

Consider the following statements with respect to Calcitonin:
$I$. It is non-iodised.
$II$. It is secreted by parafollicular cells.
$III$. It regulates the calcium level in blood.
$IV$. It is also called as $TCT$ (Thyrocalcitonin).
$V$. It is a hyperglycemic agent.
Select the option containing correct statements from the above given statements.

If the thyroid gland is completely removed from a tadpole,then :-

The $BMR$ of body cells is regulated by $........$.

Symptoms like pot-bellied,pigeon-like chest,protruding tongue,and mental retardation are characteristic of:

The largest endocrine gland is: