1. The df command can be provided with a path and it will work out the mount point on which that path lives and give you the free disk space. Ansible Facts provide disk usage statistics, but only by mount point, and so you must figure out which mount point your path lives on.
2. The find module is used to locate files.
3. Changes to configuration files might get made accidentally, maliciously, or as a result of an emergency change to fix an issue. In all cases, it is important to identify the changes and ensure that they are either removed or the playbooks updated to reflect the new configuration (especially when they were made to resolve an issue).
4. You could use the template module or copy module to copy over the file and run Ansible in check mode. You could also checksum the file and see whether that matches a known value.
5. Use...