Yes, they are awards, not advances. The second depends on sales math/how successful your COG title or the winning entry is, but potentially, yes. It's a contest. The winners will be (I think) pretty handsomely rewarded.
We all have slightly different goals in mind for the kinds of entries we receive or indeed the point, but speaking as someone who fields a lot our email, I'll say this. I've received a lot of emails which say something like "I'm not really eligible (i.e. a writer) to be considered to write for Choice of Games, but how about if I write a whole game and then you guys see if it's good enough for Choice of Games?" Our game/pitch development process is complex. It's nuanced; here we've laid the cards so to speak on the table, and are giving folks an opportunity to try to write something against those guidelines without input from us. So, good luck to all!