I don't think Prachi will get to know about the bet from Sanju, it'll either be Rhea telling her or Ranbir trying to make a confession or her accidentally eavesdropping someone. Either way, she'll be deeply hurt when she finds out, bcz by that time I'm pretty sure she'd have formed a very good bond with Ranbir. Ranbir will have a hard time winning her trust again :(
Idk about the wedding swap thing, but I have a feeling that a sacrifice track from Prachi will definitely be there once she finds out Rhea is her sister. I won't be looking forward to it at all
I m also dam sure that Bet thing will come out after Prachi-Ranbir bond become stronger .... Bet will be disclose by either Reha or Ranbir only