Can you create events for demo purposes in lieu of having inputs?

Yes. You can use 'events' such as time, or mouse cursor position. Calculation tags can do this and the Modulus function is useful.
You can also use the integrated Modbus server (there is also AB) to write to a virtual Modbus PLC register (via TCP/IP with IP address being set to PC internal or use default 127.0.0.1). You can then 'read' from that device at the same address.

While useful for demo's the Modbus Server functionality was actually created so that some OEM's could have VTScada appear to DCS's (and other 3rd party systems) as an RTU. OPC Server functionality (also built in) does the same, but some older DCS's (like in Power plants) may not support it or be restricted in its use due to security protocols.

Which AB device does it emulate and at what port?

The Modbus Compatible Device driver has a virtual IO tab where you can assign Virtual PLC addresses. Note that these values are not retained and default to 0 when you restart your application. I usually put this under a TCP/IP port with the Localhost address although I'm not sure this is necessary.