The show version command on Cisco devices provides a variety of system information, including:
Cisco IOS version: The version of the Cisco IOS software running on the device.
Boot image: The location of the IOS image used during startup.
Hardware information: Model, processor type, memory details.
Interfaces: A list of the device's interfaces.
Configuration register: The current value of the configuration register, typically displayed near the end of the output.
Why other options are incorrect:
show flash: Displays the contents of flash memory, but not the configuration register.
show running-config: Displays the currently active configuration, but the configuration register setting is not directly part of the running configuration.
show config-register: This is not a standard Cisco IOS command.