<< can the siemens switch be uplinked to a hub >>
I don't see why not...but what are you trying to do??
<< what the exact difference is between a switch and a hub >>
Copied from SMC.com -> All the devices connected to a hub are in the same collision domain. These devices share the bandwidth of the hub (10 Mbps for Ethernet or 100 Mbps for Fast Ethernet). By contrast, each port of a switch is actually the entrance to a separate collision domain with its own dedicated bandwidth. Each domain is either shared by other devices or dedicated to a single device.
In another word, your overall performance is better w/ a switch because each individual port gets the whole bandwidth.