Use what, Unity or the ToS? Assuming you meant the ToS under the old version you could stop using an updated ToS only if it violated your rights. (Which is such a weird thing to even mention, if a contract violated your rights then it probably already doesn’t apply.) You can stop using Unity whenever you want though because you have free will. Not trying to be sassy about that last point, just explaining why I think I misunderstood you lol.