2, or get a rubber band to bring the key on your wrist, which will basically not affect your exercise. If the rubber band is chosen properly, it will not fall off, even when swimming.
3, usually take a bag or pocket, put on spare clothes and change into clothes wet with sweat, decorate water to replenish the lost water in time, and decorate prickly heat powder to avoid rubbing the skin during exercise (generally not used).