No, they can't change previous moves, but in a game, the same patterns often keep on returning, and analysing previous moves can give an advantage. So if you miss something at move 22 and you find that out at move 24, it certainly helps you understand that current position better. Maybe it's not as bad as I picture it, but I'm really *beep* off by this.

I'de rather don't receive compliments in this rude form.

Thanks for your opinions!