Mr. Oberoi...I think he is playing big game here...it can be that he is having some personal issues with Amrit or her family and now he is doing things which are unimaginable for anyone...
It was shown to us that Mr. Oberoi saved Nimrit (Dimple) and then he given her new face (Ankita).
Now that Dimple is re-entering in the show.. possible story would be ...
May be for Mr. Oberoi is playing big game here for his personal benifits... His daughter..whose name given to current Nimrit (Ankita) character...is not at all real Nimrit. He might have saved Nimrit but then he kept her some hidden place..
Mr. Oberoi must have hypnotized his own daughter (Natasha - Ankita) himself or with the help of some hypnotist to the extent that she started to believe that she is the real Nimrit and forgotten her realself - Natasha.
Now the real Nimrit (Dimple) get rid or Mr. Oberoi some how and freed herself ...
May be now there will be big fight between Natasha (Ankita) - Nimrit (Dimple)... so as to prove the identity. Mr. Oberoi will surely going to play big role here...
And then Agam...who will surely feels something fishy with Natasha and Oberoi will then try and find out the truth along with real Nimrit (Dimple)...