Option 1
I think M will talk to K and tell him the entire truth(I don't know how much more truth is there for k moms death), K might feel bad and forgive him. Forget the past and move on with N.. don't know if he will accept S, don't know if he will call M papa immediately but I'm sure past track is done.
Option 2
He will come to know the entire truth and bash at S but later he might calm himself and decide to leave this matter for now for crybaby sake, not to spoil her happiness with more fights at home. He will not forgive both of them but will be normal like he always has been.
We will probably get an apology from K to N for behaving rudely for past few days and give her a romantic surprise. This time I'm sure N won't say nething to him. All decisions will be taken by him.
After this we will get fun times bachelor/hens party. The past track can end here or take a break now and to be continued after keerthi wedding or step brother track.