Is there a way to install the Device portal from Windows 10 IoT Core to Windows 10 Mobile and desktop?
I don't know about desktop, but it is actually present on mobile version. Just go to Settings, select Update & security, then For developers. Activate Device discovery and Device portal. You will see a URL address to which you can connect. After entering the page with a browser from PC, you need to enter PIN - it will be generated by your phone (tap Pair in Device discovery).