Yes – strong magnets, especially neodymium magnets, can damage magnetic bank cards and may affect smartphones in certain situations.
The risk depends on magnet strength, distance, and exposure time.

No – neodymium magnets are not safe for children and should never be used as toys.
Because of their extremely strong attraction and small size, they pose a serious risk of internal injury, finger pinching, eye damage, and life-threatening intestinal perforation if swallowed.