The revised RoHS (Reduction of Hazardous Substances) Directive 2011/65/EU...

Change the batteries as soon as the device starts malfunctioning. Remove the batteries if you plan on not using the device for a longer period of time.

There can be several reasons why the appliance doesn't work. The battery can be wrongly inserted in the battery compartment, there can be a bad connection between the battery and the compartment connection terminal or it is possible the appliance does not work properly.

Batteries are classified according to IEC classification standards: LR03 is equal to AAA, but in another standard.

Please store your batteries in dry conditions, and avoid high temperatures and direct sunlight.

Mixed use or leaving the battery in the appliance can cause battery leakage.

Typically for an alkaline battery is a gradually decreasing voltage when it discharges, which means that for some appliances, which need a high base voltage to operate, the appliance stops working even while the battery has still a bit of energy left.

Immediately head to the nearest emergency room. Avoid drinking or eating before a doctor has provided a decent diagnosis.

Do not throw batteries in the trash. You can recycle every battery type you use - even unusable rechargeable batteries. Recycling points and regulations are different in every country.

Yes. All batteries have an expiration date, beyond which their performance decreases.