CONF_modules_free() closes down and frees up all memory allocated by all configuration modules.
CONF_modules_finish() calls each configuration modules finish handler to free up any configuration that module may have performed.
CONF_modules_unload() finishes and unloads configuration modules. If all is set to 0 only modules loaded from DSOs will be unloads. If all is 1 all modules, including builtin modules will be unloaded.
NOTES
Normally in versions of OpenSSL prior to 1.1.0 applications will only call CONF_modules_free() at application exit to tidy up any configuration performed. From 1.1.0 CONF_modules_free() is deprecated and no explicit CONF cleanup is required at all. For more information see RETURN VALUE