Rachit ki parents ho sakte hai...But Rachit khud vi ho sakta hai. And Surrogacy wala jhoot vi toh pakra gayA. Ab sampu kya karegi ?
So I definitely think Atharva has his memory back and has been pretending to be Atharva beta to aviod jail. I think he saw an opportunity with Swara and he took it and married her ao that he can save himself down the line, he knows he can't pretend to be a child forever. In that regard, there are high chances that he is the one who is blackmailing Swara with those photos so that she says with him and develops a soft corner for him. Though how he got those photos from Asha and Ahir remains a mystery.
But he is definitely not the person who sent those lawyers to defend Rachit's case. Only someone wants to get revenge for Rachit's death would have sent those lawyers - doesn't seem like his colleagues in his company or his family (since they are not mentioned) wants revenge for his death so who sent these company lawyers out of the blue? I feel like my original theory about Rachit trapping Mai with his own death to get Kalyani is probably the most sensible scenario.
These new lawyers are just trying to create confusion for the judge who already thinks Anupriya is guilty so that the judge doubts Anupriya's motives. Making it out be a grab for property and money even if it is without proof it will create doubts.
As for the surrogate, I think SamChit since thye knew that Sampada can't conceive, have been planning to use a surrogate all along. So that they can hold the surrogate and the child hostage to control KalMa. Ofc they hoped SamHar wedding would happen first, but since Malhar is not budging and Rachit is supposedly dead, Sampada is still going through with that plan.