A tourniquet stops the blood flow completely, so if it stays on for long, the arm or leg will be seriously damaged. In hot weather it can be left on for up to 1 hour, and in cold weather for half an hour, because in the cold the limb is damaged faster without blood.
A tourniquet completely stops the blood flow to the limb, which, if it stays on too long, can lead to tissue death. In hot weather it can stay on for no more than 1 hour, and in cold weather only up to 30 minutes, because chilled tissues without blood circulation are damaged faster.
Option 1. The rules are reversed here: in cold weather the permitted time is shorter, not longer.
Option 3. Leaving a tourniquet on for an unlimited time would cause irreversible tissue damage and loss of the limb.