Which hormone relates with temperature and sleep-wake cycle?

From which one of the following,the melatonin is derived?

The hormone $Melatonin$ is produced by the:

The pineal gland is associated with:

The pineal body originates from:

Identify the correct gland on the basis of the following characteristics:
$(I)$ It is located on the dorsal side of the forebrain.
$(II)$ It plays a very important role in the regulation of the $24$-hour rhythm of our body.
$(III)$ It helps in maintaining body temperature.
$(IV)$ Its hormone influences metabolism as well as defense capability.