No. If you want to upload a game to Armor Games then you have to create it yourself, it doesn't matter if you upload it to another site or not, you just can't take a game you didn't create from another site and upload it to Armor Games.
Wrong. You have to be the creator, no matter what.
I'm pretty sure you can if you have written proof from the creator. Look at the ArmorGames account, it has 105 games submitted and I doubt those are all from the employees of AG.
Looked through the guide at the top and it said this: If you want a game on the site that isn't here already, you can contact the developers and ask them to submit it for you, or contact the staff and ask them to get permission to feature the game. So it doesn't look like you can submit it yourself, you have to get AG to do it.
How do I know were's the creator ? Of a random game
Let's take Kongregate and NewGrounds for example; it shows the developers name when you scroll down a little, just like here on AG, which makes it easy to get in contact with them. Though if you're talking about a site where it just has a lot of random games, I don't think you'll know who the creator of a certain game is.
but a lot of people just download the game from others sites and than just post here on AG
Armor Games has a strict screening process before games are made public. It's not like on Kongregate where you can upload any kind of game without it being tested.