what is the default user name and password of microtik CRS 328 4C 20S 4S+ router board . we also tried to reset this device by pressing the reset button but it is not working as excepted . is there any other steps available here to reset this device.
if reset button is not wprking , how to reset the device. what is the default user name and password
Is on it's label.
If no password on label = no password
Let's say, rather, that it doesn't work the way you think...
use netinstall
The reset button is not a "reset button", it is a multi-functions button that can - among other choices - reset the device.
There is a specific procedure (that allows loading either of the two bootloaders and choose among reset, CAPS mode and netinstall):
RouterOS configuration reset - RouterOS - MikroTik Documentation