Brief search does not come with anything - is there any open-source project with the same functionality as file based flex cloning?
Linux "cp --reflink" does very much the same on filesystems that support it (btrfs, I think recent XFS, ocfs2, may be more).
With cp --reflink can you delete parent of the cloned file like the one with ONTAP?
On backed implementation does it do block level cloning like Netapp does?
Answer to 1 is "yes". I am not sure what you mean with "block level cloning". "cp --reflink" creates file that shares actual data areas with source. To my knowledge that is what flexcloning file on NetApp does as well.
Thanks. Will give a try.