It's basically an LCD, not a donkey, that it will keep running with "mar kuttai". LCD is so fragile that a little bit of wrong pressing while installation could also damage it.
LCD backlight is faulty as already told and glass is also broken. Both can be replaced separately, but risky and not very cost saving over full lcd replacement. No exact idea, but it should be 3-4k.
Metal sheet > backlight > LCD > Digitizer > Glass