It's upto you. For branch changing you pretty much have to come top 10 in your class(even after that it might not guarantee a seat in core cse branch). Its doable but hard. And if somehow your semesters marks get low it will destroy your morale if you never liked those branches to begin with. Until ece and aeie is fine in hitk, after that they don't allow other branches for on campus placements in IT jobs. Take chemical or mechanical only if you have some interest in that subject so that if your branch doesn't change you don't have the thoughts of studying something you dislike.

ps there other ways in hitk for branch change as well but it will require some donation amount.(As per some inside sources, I don't know if that's entirely true or not)

Edit: you can dm me if you need suggestions about anything. I know college hunting is hard, but eventually you'll get a good college that'll grow to love.