finger prints wiped out on knife

no way!!

If Tanveer had already found the knife and erased the fingerprints than why did she go to check the box? Also, I think the CVs are finally bringing and end to the Tanveer track. So things will work in Zoya's favor now.

Knife was in inner cupboard which was locked and hence tanu didn't find it. If she found already, she has no reason to go after it to the letter box.

No you guy are forgetting Zoya put that knife in a safe in her closet, after she saw the room in a mess, if you look at the video carefully u will c that the took the keys fron on to of the closet.Tanveer had no access to the knife.