HI, Dmitry,
1.In my case, the Keyboard Reciever Switch goes gary and can not turn on whenever I experiencing the problem on Windows 8. Now I am running Windows 10 on Tap 11. No matter what kind of OS I am using, I always stay in PC mode. By the way, I disable "Allow the computer to turn off this device" on the keyboard receiver.
2.Yes, that's what I recommand because it worked for me.
3.In my case, the USB Composite Device location is
Port_#0001.Hub_#0003
The information is
USB/VID_054C&PID_0872\6&30cc556&0&1
GUID:{36FC9E60-C465-11CF-8056-444553540000}
It a pity that Sony would not face this problem and fix it.
Cybermark