As per the first BTS shiva was on stage in his normal clothes.disha and raavi both were on stage.
I think koi confusion hoga which will lead to all three of them on stage.shivi may think that they both are participating and the host will announce shiva and disha as a couple.
Shiva will have some scenes with disha.maybe she will request him to act along.they can complete one round together and win it.
Raavi will feel humilated in front of so many people and leave.
Shiva will notice this, he will decide to change for raavi tonight.he will go to green room, suit up, groom himself and will have a monologue where he will say to himself that he will fix everything tonight.he will win this with raavi.
Then When he will search raavi and come to her, she will misunderstand him that he has done all this effort for disha. She will further get angry and say some really mean things which will push shiva further away from her.
He had insecurities that such clothes won't suit him, raavi can say like tu kitna bhi suit pehen le, rahega wohi gawar hi. She will say she regrets this Marriage and some stuff like that.
Shiva will fail to understand her hurt behind this, raavi will fail to understand his efforts and intentions for her .
Just a speculation, gaaliya mat dena 🙈