Okay, this is not an essay and since I was not a regular viewer I just know the basic story. I hope someone else also posts history.
So when Krishna came to the Shukla house, there were small things that insulted.
There was this meet up where she had to point at something on the globe because Shukla wanted the society to see he has an educated bahoo.
Then Shukla and Shuklain slept outside the bedroom so that Radhay and Krishna actually have an SR - which didn't happen.
Then her father was tortured because she sent Guj to jail.
After the torture, I think Radhay and Krishna left the house. Radhay was supporting Krishna. So Shukla faked an illness and Radhay and Krishna returned. But then Shukla conspired with Krishna's ex and created zillions of misunderstanding between Radhay and Krishna. Radhay actually started doubting Krishna and threw her out of the house and was ready to divorce her. Krishna found out obviously and went back and then there was this game between Krishna and BS. BS told her she'll be out of the house before Diwali. Meanwhile, Krishna started winning the hearts of everyone and also removed all doubts from Radhay's mind.
BS conspired with Bela's mother and fixed a marriage of Radhay with Bela's sister. Radhay was also looking for ways so that he can get 30 lac rupees and send Krishna to London for her medical studies.
Somewhere at this point, the brother of BS was introduced who was crazy. He had killed his wife and tried raping Shuklain and was on a run for 30 years. And Radhay was basically his son. He returned and Shukla went missing. Shuklain was too scared to say anything to anyone. He was more of a two-faced person. He looked all sweet in front of everyone but behind the back, he was his evil self. Basically, BS was kidnapped by this guy and eventually even Radhay. Long story short (because this track was seriously dragged) Krishna ended up saving BS and Radhay and that's when BS accepted Krishna and gave all the support to her to go continue her studies in London.
The Guj story that I know of is that Guj used to beat Lalia. In the very early days, Krishna sent him to jail for an overnight. Then later, Radhay wanted to please Krishna and take her out of the city. So Krishna planned and asked him to arrange a trip to Mumbai along with Guj and Lalia. Mumbai, because years ago Guj and Lalia had planned to go to Mumbai but couldn't. That's where the two of them started understanding one another and Guj began to realize his feelings for Lalia. He had then started looking after her and stopped beating her. Cancer, only increased his love and care for her.