It is just a trap.
Situation 1:Shagun has no idea that Ashok wants to dump her. She has no idea that Ashok is eyeing Mihika. Suraj threatened Shagun that her family had disowned her. Shagun said she will fight this. Only person Shagun told to keep eye on Ashok is Param
Situation 2: Ashok wants to teach a lesson to Shagun by dumping her. He too has confided in Param. Ashok has no idea about Shagun's plan.
So Param is the only person who knows about Ashok's plan and Shagun's plan. Plus Param is enemy of the bhallas who is in the Bhalla house.
Shguan wants to prove that she has family. She wants Mihir's support I guess since Mihir had disowned her. Shagun , Raman, Mihir are thinking that the Iyers will not allow the marriage if they know about Mihir's past. So what does Shagun do... she hatches a plot to bring back MIhir. She knows as long as MIhir is with MIhika, he will not come back. Hence she is plotting to break up Mi Mi. She thinks that way she will comfort Mihir and get him back in her camp. Shagun must be in touch with PP. And Shagun must have planted Sanjana in the cooking class. She wants Ishita to know the truth about Mihir. Shagun thinks Ishita will reject Mihir if the truth comes out. Param is acting as her agent. If Mihir comes back, Shagun wins against Suraj and can marry Ashok.
On the other side, Ashok too wants to break up MiMi because he wants to marry Mihika.
Surprise will be when Shagun will come to know about Ashok's plan.
After that Shgaun may get disheartened and talk to Adi. Adi may tell RKB that if he wants his custody, then he must take Shagun back. I think Ishita might hear this. She may assume that RKB will leave her. This was Toshiji's fear about "badi galti" will play in Ishita's mind. She may want to do mahan tyag which may lead to RKB's confession.
On the other side, both Shagun and Ashok might become desperate to break up the marriage. Hence they might go to the mandap and try to stop the wedding at the last moment by revealing MIhir's past. Iyers will get angry. But Ishita will make them understand.I think MiMi marriage will happen.
RKB's confession part may happen after Mimi wedding...don't know... but this is what I could think of depending on what they are showing now. Somewhere in all this, Param's truth might get revealed.