Is Miscalculating Menstrual Purity a Sin in Islam?

If she had an IUD inserted, then her period got longer, then she suffered prolonged non-menstrual bleeding, should she follow her cycle before the IUD or after it?

She had some secretions in which there was a thread of blood

Her period became irregular because of taking pills to prevent menstruation; what should she do about prayer and fasting?

Can ghusl from janaabah also count as ghusl following menses and vice versa?

She thinks it most likely that her period is coming; is it permissible for her to delay the prayer and not do it as soon as the time for it begins?

A woman with istihaadah (irregular bleeding) who had a regular cycle should stop praying at the time when she used to get her menses, whether at the beginning of the month, in the middle or at the end

Her nifaas is intermittent and the bleeding is very light. Should she fast?

The post-partum bleeding (nifaas) stopped, then she saw some drops of blood; what is the ruling on her fasting in that case?

If someone is sick and unable to move, and the time for prayer comes and it is not possible to do wudu and pray, what should he or she do?