Well I must say Adi is the most unlucky person in this world! He isnt perfect, has many flaws just like us but he is surrounded by people who can potentially forever remove his faith on love and family!
His father who can manipulate anyone ,
his mother definitely has a lot of shades behind this avatar of her,
his brother , who reads his bhabhi's diary , silently gives it to stranger but can't tell his brother, we assume that is doing all this so that his brother can get closure but technically in the story, he is doing all of that coz he is mahaan and sachai ka murat,
his wife, rather confronting him that she isn't happy with him and needs to move out, she chose to cheat right under his nose and had the nerve to tell Adi that nobody shares everything with everyone,
his mother in law who had the nerve to support her daughter after her lies were caught and not while her daughter was shamelessly cheating her son inlaw,
his friend whom he saved multiple times, ah yes she saved his whole family right so scores equal, but yes that friend who wants to reopen the case not for Adiya but only Zoya. She being the righteous lady, doesn't really mind using someone's personal diary to prove her dead husbands innocence! Nice hypocrisy.
Guys lets not assume, that a person is doing all this to get closure, its an interesting twist etc... lets only go by what is being shown and discuss. Each person has their own way of seeing things, so by saying Arjun wants a closure for his bhai, doesn't makes sense to me as long as I don't see it in the same way. So lets go by only what is shown already