Nikaah & Marriage Issues

Q: My question is related to khalwat e sahiha. 

If a couple used to meet in the guest room of the wife's house whose doors were usually closed but they were never locked. They usually used to meet in the presence of the mother in law who used to come in the room in phases, at times by knocking and at times she would knock and open the door slightly so that the couple knows that she's coming. There was always a risk of her entering. The couple used to be physically intimate (sexual intercourse never happened) but there was always a fear of her entering because the door didn't have a lock. Would this be considered khalwat e sahiha or not?

Q: I am writing anonymously on behalf of my friend, who seeks guidance regarding a sensitive matter. 

Two years ago, when she was around 14–15 years old and her partner was 15–16, they performed a nikah with witnesses present. It began as a joke for their 4-month anniversary, but the full nikah words were said in front of 3 witnesses: 

The friend asked: “Do you, [his full name], take [her full name] as your wife?” and vice versa 

He replied: “Yes, I take [her full name] as my wife.” 

She also said: “I take [his full name] as my husband.” 

At the time, they did not fully understand the seriousness of their actions. They later consummated the marriage when she was almost 16 and he was almost 17, still unaware that it counted as a valid nikah. 

Now, she realized the marriage may be considered valid in Islam, but she is unsure how to handle the situation given their young ages at the time, the accidental nature of the nikah. 

They seek guidance on: 

1. The Islamic validity of the nikah given their ages and circumstances at the time. 

2. How to properly formalize or rectify any steps (including mahr, witnesses, or scholarly confirmation). 

3. The correct way to proceed if they wish to continue the marriage safely and according to Islamic law. 

Your advice would be greatly appreciated so that everything can be handled properly and responsibly.

Q: A man had previously asked me to marry him in the presence of two witnesses and I said yes. This was years ago. 

My husband currently went through my phone and saw a chat regarding this marriage. He asked me about it which I said it was invalid as it was not conducted with a wali. My husband said it is valid. After having checked a Muslim girl can marry herself without a Wali. 

My husband promised marriage to me again if I take a talaq from the previous boy which I did and then he, my current husband will make a new nikkah. 

After doing all of this, all of a sudden my husband current gave me a third talaq. Now we are in a dilemma as to whether I can make nikkah with my second husband again as his nikkah with me was not valid.