Normally you can restart/replan up until the target is killed and if you are beyond that point the restart/replan options no longer function.
But here’s what happened to me: I approached the elusive target, pushed the button to throw him off the balcony but immediately hit ESC, he had not yet gone over the railing, he was not dead and had no indicator in game that he was dead yet. On the ESC screen I was able to restart/replan.
I hit replan because I realized I had been spotted (and I’d restarted several times before that without issue). Because the replan button still worked I assumed I was safe to use it. In Hitman (2016) if you were beyond the restart/replan ability you wouldn’t even be able to push those buttons.
So I replanned, as I’d done several times before, but this time it said I had failed and I was not able to do the target.
Now I understand if restart/replan had been disabled that I’d have at least had a chance to leave the pause menu and finish the mission without a silent assassin rating. But the game let me restart and in game it didn’t look like I’d actually killed him yet, yes I had hit the button to push him but he wasn’t even over the railing yet, he wasn’t dead
But the replan button basically failed the mission for me. I’d consider this a bug, if the game thought I’d already killed him I should not have been able to replay/replan at all and I would have unpaused and made my way to the exit with a lower rating.