Woman seeing a brown discharge after 10 days of haidh

Q: I usually get my haidh for 10 days, with the last 4 days typically being just light brown spotting here and there. 

This month, on the 7th day, I noticed clear discharge. By the 9th day, I realised that since then, I hadn’t seen any discharge, so I assumed my haidh had ended. I performed ghusl and made qadha of the missed salaah. 

Later that same day, I noticed a small amount of clear discharge again, with a very tiny yellow dot.

When the 10 days were completed, there was still no more discharge. However, after the 10 days were over, I noticed a small amount of brown discharge. 

Do I need to perform another ghusl? Or did my haidh end on the 7th day?

Ruling regarding a woman who emits a discharge throughout the month

Q: What is the ruling regarding a woman who emits a discharge throughout the month? 

For ±3 days before and after her haidh it is brown in colour. Her bleeding lasts for ±8 days . During the rest of the month her discharge is yellow or white. 

If she regards all coloured discharges as haidh then those days when she is actually bleeding may fall under istihadha?

Hurmat-e-musaaharah not being established by touching one's grandmother or uncle's wife

Q: 

1. If a man touches his maternal grandmother with lust, does the marriage of his mother with his father break? 

2. If a man touches his paternal uncle’s wife (Chacha’s wife) with lust, does his paternal uncle’s marriage break? 

I am dealing with a lot of thoughts about hurmat musahara.

Wife taking her husband's surname

Q: I have heard that you are not allowed to take your husbands surname after getting married according to these verses: 

"Call them by their fathers names; that is more just in the sight of Allah. (Quraan 33:5)" 

The Prophet (sallallahu alaihi wasallam) said: "Whoever claims to belong to someone other than his father has committed an act of disbelief. (Sahih Bukhari 3508, Muslim 61)". 

a. Are these quotes correct? 

b. Is the statement you're not allowed to take your husbands surname after marriage correct? 

c. I know of people who have registered themselves for marriage at Islamic centres and they have asked women if they want to take their husbands surname.