Cannot rename resolv.conf file as root

As per your steps, you protected the file /etc/resolv.conf from being deleted/overwritten with chattr +i (immutable)

So, you won't be able to move it to another file without doing sudo chattr -i /etc/resolv.conf first.

From man chattr

A file with the 'i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.