Haiz, Istihaazah & Nifaas

Woman seeing yellow discharge before and after the days of haidh

Q:

1. I learnt that a female's yellow discharge is regarded as haidh during the day's of haidh and istihaadha out of it. Therefore, if one experiences this discharge before the fifteen days tuhr is up, sometimes just a few days before haidh begins and sometimes through the tuhr period, does one need to treat it as normal istihaadha, i.e. change and make a fresh wudhu for every salah, or as normal discharge, i.e wudhu only breaks when the discharge comes out?

2. Regarding the yellow discharge, if the lady gets it after 11 days of tuhr and it continues till the 16th day, and thereafter she gets her normal haidh (proper bleeding that usually lasts for about 8 days and if counted with the yellow discharge would go over 10 days), but her habit is normally 18 days of tuhr, does she count her haidh from the 15th, 16th, or 18th day?

Irregular haidh

Q: In November, I had a tuhr period of 15 days. Then I had haidh from 17 to 27 November. After that I experienced bleeding for 10 more days but I prayed my namaz. Then there was no bleeding for 6 days. From 13 December, I started my haidh again which continued till 23 December. After that I was clean for 8 days but again started bleeding from 1st January. Now how will I calculate my tuhr period now? Will it be 15 days? When will I count my next haidh?