Is it permissible to continue using the IUD (intrauterine device) for contraception after learning of its prohibition for those who are not in dire need, especially given the absence of another safe alternative? And are the intermittent brown discharges at the beginning of the menstrual cycle considered istihadah (irregular bleeding) that necessitates prayer?

It is not permissible to insert an IUD except out of necessity or need. It should be removed if there is no longer a need for it. As for brown blood spots, if they appear before the onset of bleeding and continue with it, and their total duration combined with the subsequent bleeding does not exceed fifteen days, then it is menstrual blood (hayd). If it exceeds fifteen days, the woman has the choice between distinguishing (good from bad blood) or reverting to her customary period. However, if these spots appear after the cessation of bleeding: if they appear before fifteen days have passed since the beginning of the bleeding, then it is hayd. If they appear after fifteen days from its beginning and before fifteen days from purity (tuhr), then it is corrupt blood (fasad). If they appear after fifteen days of purity, then it is a new hayd if its flow continues for a day and a night; otherwise, it is corrupt blood.