There are many myths about Demeter, from the most well known of her daughter Persephone being kidnapped by Hades and becoming his Queen, and Demeter's search for her and then finding and Persephone's yearly travel between the Underworld and Earth, to which the ancients credited to being the cause of winter (death) and spring (life) of growing things, as both Demeter and Persephone were goddesses of the earth and growing life.
Among the myths, while she wandered, one tells how she nursed the child Demophoon, son of King Keleos and Queen Metaneira of Eleusis; she would have made him a immortal god but Metaneira saw her putting the child in the flame and feared for him, speaking rashly, and Demeter heard her and heeded her, her task unfinished.
Triptolemos was another such prince of Eleusis (though less clear is his parentage) who Demeter favored for having welcomed her, she gave him the secrets of agriculture and told him to share them with mankind, to better do so she gave him a winged chariot drawn by serpents.
There are other myths, of course, but I give a small example of both the well known and less so that you have a wider idea of what happened to Demeter in some of the myths in Greek mythology.
They wither away.
Nothing: there is no surviving myth which makes Aphrodite or Demeter companions. In fact, Demeter would have much reason to dislike Aphrodite for making Hades take away Persephone (her daughter) for wife.
When Demeter mourns for her daughter Persephone, the earth experiences winter as she withdraws her fertility and stops plants from growing. This period is known as the "winter season" in Greek mythology and symbolizes Demeter's sorrow and grief.
In Greek mythology, Demeter is the goddess of harvest. Her daughter is Persephone. Hades is the god of the underworld and he kidnapped Persephone. To make a long story short, there was an agreement made between Hades and Demeter to share Persephone. When Persephone is with Hades, Demeter is so sad that nothing will grow and that is why winter happens.
There was no "god of Demeter", Demeter was a Greek goddess.
Demeter
In the Spring, Demeter's daughter, Persephone, returns from the Underworld to spend the Spring and Summer with her mother. Demeter makes the Earth bloom and growth beautifully during these seasons. In the Fall, Persephone must return to the Underworld to spend the next six months with Hades. Out of despair, Demeter, as the goddess of agriculture, refuses to cause the Earth to sprout living things during the Fall and Winter.
Demeter was not married. Demeter had two consorts in Karmanor and Iasion.
Demeter was older. Demeter was born of Cronus and Rhea. Her brothers were Zeus, Hades, and Poseidon. Since Artemis is a daughter of Zeus, Demeter's youngest sibling, Demeter has to be older. This also makes Artemis Demeter's niece.
Demeter is a girl. Demeter was a Greek goddess of agriculture.
demeter
No. Demeter is a Greek name. The Roman name for Demeter is Ceres.