You can use Netinstall to re-flash the firmware. It's only adding some very basic configuration to the router iirc.
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No they are baked into the firmware.
You can see all default config scripts in the docs here: https://help.mikrotik.com/docs/spaces/ROS/pages/167706788/Default+configurations There are different scripts for different devices
Or on a terminal you can even print the exact script which runs if you don't enable "no default config" on reset:
/system/default-configuration/print
Be careful, if you reset without default config, the DHCP client and server won't start automatically, so your device won't have an IP address, so you have to connect with Winbox via MAC address