Check the sticker on the back or bottom of your device for the manufacturer (e.g., Zyxel, TP-Link, ZTE) and the exact model number. The BCM63381B0 chipset is used by several brands, and using the wrong firmware can permanently damage ("brick") your device.
For the chipset (commonly used in xDSL residential gateways), a notable "useful feature" often sought by developers and power users is the extended command set available in its CFE (Common Firmware Environment) bootloader. Key Functional Features bcm63381b0 firmware full