We're not going to be so stringent as to ask for your .capx's.
The limitations AFAIK are basically that you are limited to 100 events, and max 4 layers.
So if you give us a game with 6 moving parallaxes and like 6000 dudes running around on the screen, we MAY have to disqualify you (or ding you a lot of points ... Not sure which I'd prefer to do, I guess it depends on how many successful entries we get).
The limits to the free version are 100 events, 4 layers, no families or preview on LAN.
But there is a flaw in your reasoning there Venetia, it would be perfectly possible to have X layers of parralax in actually a single layer in C2, so a game proposing this wouldn't necesseraly have been done with the full version.
Same thing for the 6000 dudes moving on screen.
Especialy since you allow for the use of custom plugins.
In theory the game could be all coded in a plugin and interfaced to C2 to use the less events possible.
Apart from checking the actual capx, I don't know how to make sure an exported project was made in the free version.