Is it possible to have virtual address ip existing without a virtual server??? I saw such an ip existing in version 10x and 11x devices in virtual addres list of device GUI.
A virtual address is created when you create a virtual server with a unique IP address. In other words, if you have 3 virtual servers with the same IP and separate ports, the virtual address will only be created by the first virtual server creation, and is similar to the way nodes are created when a pool is created. If you've seen a virtual address in the GUI without a corresponding virtual server, the likely cause is that the virtual server was deleted and (for whatever reason) the corresponding virtual address was not also deleted. You can technically create a virtual address from the command line:
tmsh create / ltm virtual-address [ip address]
About virtual servers and addresses link
One way to get this is change an ip address for existing VS, an old virtual address remains in the configuration.