linux + how to identify if file is pointed by link/s

A symbolic link is similar to a shortcut in Windows. It's a entry in the file system that points to another file. The destination file is not touched and no change is made to the original files metadata - it does not know that it has been linked to.

You will not be able to tell if a file has symbolic links pointing at it just by looking at information from ls.

Hard links, however, increment the link count on the file system which can be seen in a directory listing. If you hard link two files to the same data, both will show a link count of 2

what the way to identify if file or directory have link/s

You can do like this:

find / -lname "filename"