[Plugin: WP Super Cache] [at least] super cache installed in mu-plugins do not uninstall properly.

hello. i have installed super cache to mu-plugins directory. official instructions for uninstalling do not work. I copy them here, for the current version will be saved here:

== How to uninstall WP Super Cache ==

Edit the file uninstall.php in your plugins/wp-super-cache/ directory and set
UNINSTALL_WPSUPERCACHE to a non blank value.

define( 'UNINSTALL_WPSUPERCACHE', '1' );

Open your browser and load wp-content/plugins/wp-super-cache/uninstall.php directly.
You must be logged in, and you must confirm the action. If you do not delete the plugin
immediately, after the script runs, please comment out the define() above to stop
someone else running it.

To manually uninstall:

1. Remove the WP_CACHE define from wp-config.php. It looks like define( 'WP_CACHE', true );
2. Clear the cache in the backend page and then deactivate the plugin on the plugins page.
3. Remove the Super Cache mod_rewrite rules from your .htaccess file.
4. Remove the files wp-content/advanced-cache.php and wp-content/wp-cache-config.php
5. Remove the directory wp-content/cache/
6. Remove the directory wp-super-cache from your plugins directory.

1. wp-content/plugins/wp-super-cache/uninstall.php has not worked and i have gone to manually uninstalling. only later i have understood that had(?) should replace plugins to mu-plugins.
2. 2nd item of manually uninstall does not work because commenting out define( ‘WP_CACHE’, true ); as said in 1st item, so i uncommented it back and cleared cache. And there is no deactivate button in case of mu-plugins directory used! after all wordpress shows blank page but only says please create wp-content/wp-cache-config.php .
3. then i have tried to use uninstall.php, found and set to 1 UNINSTALL_WPSUPERCACHE , runned it, it said it deleted files etc, even e-mail has come that super cache is uninstalled, but after this again same error about wp-cache-config.php . i had to recreate that file again. after recreating this file wp works, but super cache menu item in dashboard is not deleted.