Changed blog directory, lost access

Update:
The site sort of comes up, but unthemed, and the login doesn’t work, but results in an error message:

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

I tried editing the functions.php file according to directions in https://codex.www.ads-software.com/Changing_The_Site_URL
That resulted in an error message about the functions.php file.

I tried editing the index.php file according to https://www.ads-software.com/support/topic/cant-login-to-admin-panel-after-changing-blog-address?replies=8
That resulted in the same error as the first one.

However, following the excellent instructions at https://educhalk.org/blog/2008/12/changed-wordpress-blog-address-in-settings-locked-out-how-to-fix/ worked. (I edited database through phpMayAdmin