Can I rename device name so I can access with another url (default : http://mycloudpr2100/)
I would like to recommended you read the My Cloud User Manual
It explains many of the options, including how to change the network name for the My Cloud. In particular Chapter 9, Configuring Settings, Device Profile. Or see the Help within the My Cloud user interface for more information on how to change the name.
To change the My Cloud name, log into the My Cloud Dashboard, then navigate to: Settings > General > Device Profile >Device Name. You can then change the My Cloud name to some other value.
Note: When you change the name, you will have to use that new name from that point forward to access the Dashboard. Any Shares mapped under the old name may be broken. WD Sync, Smartware, and any other programs that rely on the My Cloud name may also stop working properly until updated with the new My Cloud name.