What are some benefits of voluntary exchange? What are the responsibilities?

Hanna intends to give her granddaughter, melodee, her antique hat pin. this heirloom has been kept under lock and key in the wall vault in the library of hanna's house in virginia. the hat pin is currently the only item in the vault. when hanna is visiting melodee in connecticut, hanna gives melodee the only key to the vault. melodee is grateful for the present and excitedly accepts. in this situation has there been a completed gift?

Awidower devised his fee simple interest in his residence as follows: “to my daughter for life, then to my oldest grandchild who survives her.” at the time of the widower’s death, he was survived by his only two children, a son and a daughter, and by one grandchild, his daughter’s son. a short time later, the daughter together with her son entered into a contract to sell the residence in fee simple to a buyer. the applicable jurisdiction continues to follow the common law rule against perpetuities, but has abrogated the rule in shelley’s case. at the closing, the buyer refused to purchase the residence. can the sellers compel the buyer to do so?

What is a sort of auction for stocks in which traders verbally submit their offers?