Haiz, Istihaazah & Nifaas

Woman bleeding more than ten days

Q: I am very confused as to when I should be praying again after menses. My bleeding goes beyond 10 days every month. It doesn't stop. I sometimes see yellow discharge. I see only little traces of blood and not a proper flow. I also sometimes see water looking liquid which I am unsure to whether it is discharge or sweat or water. do I follow the rules of ishtihada and start praying after 10 days or do I resume prayer earlier? If I made a mistake and was unsure about when I should start praying, do I need to make the prayers up? 

Calculating haiz when in istihaazah

Q: In the case of istihaaza, if my period starts at around 4:00-5:00, then after my haiz days I then count 15 days as clean, now I am still having discharge like 2 times a day. So if I see any discharge at approx 4:40,will my haiz start? This is because I dont know the exact time my haiz had started last time, it was around 4 to 5 o clock... So it could be after 4:40 also.

Is it important that my counting should go in exact hours and minutes or can there be a difference of half an hour or so? I have counted the above scenario as my period. Is it okay?

Doubting whether haidh has ended

Q: Toward the end of a menstrual period, often it is not clear if the period has ended or not. This causes a frustrating problem: should she wait until she is sure the period has ended, even though she is risking missing a prayer, or should she make ghusl and pray even though it is possible the period has not yet ended? You see, if she chooses to be cautious, often she has to make multiple ghusls until she is finally sure.

Reason for mutahayyirah performing salaah as a precaution

Q: It is mentioned in a fatwa regarding a mutahayyara that if she is in doubt as to whether her haidh has ended or not, she will take ghusl for each salaah time and perform the salaah of the time. When the next salaah time comes, she will take ghusl and before performing the salaah of that time she will perform the last salaah again as a precaution" So what does it mean as a precaution perform the last salaah again. How is that being cautious?What are they being cautious of?