The iddah of a divorced woman is three durations of purity between the menstruation periods, the first of which is when the divorce takes place. The waiting period ends when she sees the menstrual blood for the third time after the divorce.
Wearing the ring in a chain around one’s neck by itself is permissible, unless doing so is considered to be imitation of women or it leads to humiliation or similar results which are prohibited to bring about, in which cases it becomes impermissible.
Divorce has a number of conditions for it to be valid; one of them is the recitation of the divorce formula like “Anti Ṭāliq” which means “you are divorced”. The recitation should be in the presence of two ʿādil witnesses Another condition is that the woman should not be in her menstruation period. If these conditions are met, the divorce is correct. If one of them is not met the divorce has not taken place and the woman is still his wife, and therefore she does not require a new marriage contract in order to return to her marital relationship. She then can return to her husband without any doubt.