Must the phone be charged to 100% before the charger can be unplugged?

It is not necessary to charge to 100 before unplugging the charger. Modern smartphones generally come with smart charging protection devices, which do not charge continuously to avoid overcharging even when charging to 100%. Therefore, when the phone reaches the required battery level, we can safely unplug the charger and start using the phone. In fact, overcharging can actually be harmful to battery life, as it may lead to a shortened battery life. Therefore, it is recommended to start charging when the battery level is close to 20% and avoid exceeding 100% during charging to extend battery life.