Usually we use the one with four carpsels. It is the one with four carpsels that are most usable. They are used for both good and bad medicines. By introducing them to the child, we pray for the child not to use it negatively against anybody neither will anybody use it negatively against him. This has the same reason as the colanut above.
Obi is used to symbolizes long life in a marrige.
It is wishing the couple a long life together. It is broken and passed around to all the well-wishers present for the ceremony. Everyone takes a small bite.