Prashant is an inevitable chapter thats waiting to be closed for Aarti. He deserted her but has never known Ansh. Its very likely that when is back in town, he will have a legitimate visitation rights over Ansh. The question then is, is it fair to Ansh to deny him the right to know his biological father, as much of a rat as he was. There is a lot of ground to cover there.
As for Sr Scindhia, I think the most logical explanation for this Arpita madness for him would be if he was advised by Yash's psychologist (after Arpita died) that Yash really needs to move on and the obsessive person he is, one way would be to saturate his conscience with Arpita. Therefore, Sr Scindhia collaborates with Arpita's parents and insists on changing Aarti's identity. This last bit is extremely unfair to Aarti and has nascent similarities to the Waheeda movie 'Khamoshi' where she takes up a persona to cure her patients but then becomes deranged herself...
Whew, that was a multiple thought rant :)