Again, if the revoke IP address is not free, and not being used, then it's possible to get the same IP address. The only way to test this out would be to disconnect the one device, revoke the IP address, then connect a different device and see if it gets that same IP address from the 1st device or not.
Host names get populated by the HOST NAME information comming from the device. If the HOST NAME isn't entered into the PC, i.e. windows then they will be blank. Some devices don't support this naming option so they will be blank and the only ways of find out what IP addresses are in the list would be to turn everything off accept for one PC, get it reserved, then turn on the next device, reserve it and do this until your done. Yes you have to give a NAME when you reserve it so it can give it anything that you see fit, I use names so I know what the devices are. It's pretty easy. You can also look on the devices and see the network IP address on the device, there you can tell what the device is by comparing it to the list.