I am confused about the iddah mentioned in Surah 65:4. Allah says: "Those in menopause among your women, for them the iddah, if you have doubt, is three months; and for those who have no courses". Ibn Kathir says: "Allah the Exalted clarifies the waiting period of the woman in menopause. And that is the one whose menstruation has stopped due to her older age. Her iddah is three months instead of the three monthly cycles for those who menstruate, which is based upon the Ayah in (Surah Al-Baqarah). [see 2:228] The same is the rule for the young, who have not reached the years of menstruation. Their iddah is three months like those in menopause.
However, in Surah 33:49 Allah says: "O you who have attained to faith! If you marry believing women and then divorce them ere you have touched them, you have no reason to expect, and to calculate, any waiting period on their part."
So my question is, if you have not had relations with them there is no waiting period, if they don't have a cycle (due to maturity according to Ibn Kathir) then you have to wait three months? Does this mean it is okay to have relations with prepubescent girls? Also what are you waiting for in this time if the girl doesn't get a cycle to begin with? Something doesn't add up for me and I am sure it is due to a misunderstanding on my part. I hope you can clarify this for me.
According to the Holy Qur'an the waiting period for women in general is three menstrual cycles. The question arose what to do with the women who are in menopause and also the ones who have reached the age of menstruation but due to some reasons their menstrual cycle has not yet started? This is clarified in the verse you have quoted in the beginning (Q 65:4).
You are also right in concluding that the waiting period is only prescribed for the women with whom marriage has been consummated. If marriage is not consummated then there is no iddah. This means that the only purpose of the iddah is to ascertain whether a woman is pregnant or not. If she is pregnant then the iddah is extended to the time of delivery.
Since women in menopause and the ones who have not yet menstruated can get pregnant they are required to wait for three months instead of three cycles so that the status of their womb is clear.
As for the question whether Q 65:4 implies that we can marry minor girls we believe that it does not. The Qur'an uses the words lam yahizna which means they have not yet menstruated. It means they are expected to have experienced menstrual cycles but have due to some medical problem not started yet. This means that the reference is for the women of age and not to the minor girls. For detail please refer to: http://monthly-renaissance.com/issue/query.aspx?id=728