This feature should be . Unauthorized access to routers is illegal in most jurisdictions. If building this as a tool, include:

user

No. Each ISP (TOT, Telkom, MTN, etc.) loads custom firmware with unique default credentials.

Older firmwares have a known vulnerability where visiting http://192.168.1.1/cgi-bin/backupsettings.conf downloads a config file containing plain-text passwords. However, most TOT routers have patched this.