There’s nothing wrong with uploading Stencyl-created games to Kongregate. In fact, Kongregate sponsored at least one game that was made entirely in Stencyl.
That said, I’d say that the OP’s game is good for a first game, but it does have problems. I don’t like the fact that you can’t jump on a platform if you collide with its bottom side. Most other platformers allow you to jump from under a platform. I’m aware that this is currently a problem with Stencyl, but there are ways to work around it. If you search the Stencyl forums, you’ll find some workarounds that aren’t 100% perfect but may suit your needs.
Also, I find it frustrating that if the screen moves faster than the avatar, he dies. I was not aware that this was how you intended the game to work until my character died a few times. Regardless, there is no logical reason why a camera that pans faster than the avatar can move is dangerous. I’ve seen games where the avatar tries to run from tidal waves and a huge stream of lava, and not being able to outrun it makes sense. A killer camera does not.
You may want to include an in-game tutorial. Simple instructions that tell players to use the arrow keys to move will suffice as long as they are presented at the start of the game. Being able to double-jump should also be explained.
Anyhow, congratulations on a good first attempt at making a Flash game. The artwork looks original and decent, which is a plus. It’s certainly much better than what most programmers can come up with. Keep making games, and you’ll get better at it.