This method requires your current admin password. If you forgot it, use the physical button method (Method 1).
Press and Hold
If you know the admin password (often the same as your WiFi password) but want a clean slate: How to Hard Reset XIAOMI Mi WiFi Router 4C
Q: Will a hard reset erase all my data? A: Yes, a hard reset will erase all customized settings, including WiFi network names, passwords, and other configurations. This method requires your current admin password