Sitting for tashahhud in the first rakaat of Zuhr Salaah and making sajdah sahw

Q:

1. I was reading 4 rakaats fardh of Zuhr Salaah. After the first rakaat, I sat down and started reading tashahhud. I realised my error, but I completed the tashahhud, stood up and after the second rakaat did the tashahhud again and completed the rest of my salaah as normal. I did a sajdah sahw at the end, but I didn't recite the tasbeeh in the sajdahs. Is my salaah valid?

2. Previously, I was also reading 4 rakaat fardh of another salaah. In the second rakaat, after reading Surah Fatiha, I untied my hands to go in ruku. I quickly realised my mistake, tied my hands again and read a surah and continued the rest of the salaah as normal. Was I meant to read sajdah sahw in this situation?

Dua to be recited by the newly wed spouses on the first night

Q: I would like to know about the prayer that the bridegroom and bride pray together after nikah and before consuming their marriage. How is it performed and why? I will be getting married soon and have heard about this from an old person and he has not been able to give me more details. All the others to whom I have asked, no one knows about it.

Sitting on a sofa which was messed with urine

Q: My wife is suffering from a serious disorder about purity. This is all due to urine.

If a child has urinated on a sofa and if someone sits there after its dried without being cleaned, will the other person be impure? Does he/she have to change their clothes?

If he/she sits somewhere else with those same clothes, would that place also be impure?

My wofe is really not well because of this and she’s always washing things, beds, clothes. etc. 

Receiving items of inheritance as a gift from the heirs of one's friend

Q: I am an expat in Saudi Arabia. One of my friends passed away here last December and his family had to move back to India. They sold most of the major items and got money and the remaining smaller items they gifted to others (Example: dinner plates, a wall clock, 3 unanimated wall hanging sceneries, etc. they gifted us and few items to others also).

Is it Ok to keep and use those items or must they be donated in charity? We are not need in need of those items and we just kept those items because we were very close to that family. What is the better option?