How to take control of the router knowing the password from the admin panel?

Question

WiFi

The password from the WiFi network and the login password from the admin panel of the router are known. How can you retain "ownership of the router" even if the owner of the router (admin) changes the password for the WiFi network or resets it to factory settings? Wpa is not an option, because you need physical access to the router.

Answer 1

Come to the owner and buy the router from him.
Well, what a question - if he is the physical owner, he can always reset all your settings manually.

Answer 2

Install custom firmware containing a backdoor on it.

Answer 3

and in more detail?