Who is the god Io?

Io. Io, in Greek mythology, daughter of Inachus (the river god of Argos) and the Oceanid Melia. Under the name of Callithyia, Io was regarded as the first priestess of Hera, the wife of Zeus. Zeus fell in love with her and, to protect her from the wrath of Hera, changed her into a white heifer.

Rest of the in-depth answer is here. Keeping this in view, who turned Io into a cow?

The daughter of the river god Inachus, Io was a priestess at one of Hera's temples. Zeus fell in love with her and seduced her. When Hera learned about Zeus's behavior, she turned the girl into a white cow. In some versions of the myth, it was Zeus who transformed Io into the cow, to conceal her from Hera.

Similarly, what is the name of Zeus and Io son? Io bore a son, Epaphus, and a daughter, Keroessa, from Zeus. According to mythology, Epaphus later founded the town of Memphis in Egypt, which he named after his wife. Keroessa mated with sea god Poseidon and gave birth to a son, Byzas, who would later found the town of Byzantium, now known as Constantinople.

In respect to this, what happened to IO in Greek mythology?

Io escaped across the Ionian Sea to Egypt, where she was restored to human form by Zeus. There, she gave birth to Zeus's son Epaphus, and a daughter as well, Keroessa. She later married Egyptian king Telegonus.

Is Io a nymph?

IO was an Argive princess and Naiad-nymph who was loved by the god Zeus. When Hera suddenly interrupted their tryst, Zeus transformed the maiden into a white heifer. However the goddess was not so easily fooled and requested the animal as a gift. She then appointed the hundred-eyed giant Argos Panoptes as its guard.