Okay , here I gonna post what I feel..
1. Kidnapper is Lakshya, he is using kidnapping drama to frame Sanskar , as though Family members first doubting on Swara, Lakshya ji himself will take a major role to make it sure that Sanskar becomes the ultimate situation2. Sanskar will doubt on Lakshya and he will be out at 11 pm in night just to collect evidences, but his this action will be used against him.3. Sanskar will be partially or completely successful to realize who the culprit is , and to stop him from revealing the truth further , Lakshya will blast his car , I don't think it's only Ragini or It's Ragini actually because there was also a news that Ragini would kidnap herself but that is not the case so I don't think Ragini will do that car-blast in reality, she wanted to give Sanskar pain , she never wanted to kill him ,she wants Sanskar alive to hurt him more in future actually , but Lakshya has reasons to do so if sanskar gets to know about his reality4. Agnipariksha means swara's attempts to save Sanskar from the trap of Lakshya (or kidnapper) , Sanskar will be badly framed by Lakshya , and Swara will act as if she is doubting Sanskar only to win the trust of the real culprit , Lakshya will fall in this trap and will try his best to manipulate swara against Sanskar and that will confirm Swara's doubt on Lakshya, and on that Agnipariksha day Swara will sense something bad gonna happen with sanskar and her instincts or her dhaaga will be savior for Sanskar , it's a symbolism of Swara's love for Sanskar which will keep him safe from all evils, I am remembering what Sanskar said on Diwali day "Tum ihann nahi Rahogi toh kaun bachayegi Mujhe?"