Running 640x960 (portrait) screen on 1366x768 PC screen
I use the Ultimate Fullscreen extension for this. I set it to go to full screen and fit to height. Since the object isn't supported by iOS it has no effect on the exported project.
There's also the option to shrink the window size with the window control object at the start, so long as resize display to fit is selected.
Running 640x960 (portrait) screen on 1366x768 PC screen
Strange, on mine, device model comes up as "" on PC... Unless they have changed it?
Running 640x960 (portrait) screen on 1366x768 PC screen
While poking around in the runtime's code for help with extension development I spotted that the mobile utilities object is supported by iOS, it doesn't do much but the condition "Is mobile" returns YES on iOS, so you could use that and negate it.