Without narendra's killing, the story would not have reached the flashpoint. As rasika cant kill narendra by herself, she needs a man to do the deed. But nowadays, women easily kill.
and it will be easy to catch rasika if she is celebrating with brijesh. It can be recorded. Or brijesh's role can be questioned in the court.
Brijesh's anger against shiv maybe professional rivalry or some old feud involving some misdemeanour by brijesh caught by shiv.
Or brijesh maybe gunning for anup through his son.