Okay, here's what I'm finding with playing the game:
I played level one first, had no clue what I was doing, and sunk close to right away. I thought "oh cool, they give you a code even if you lose", true they do, but it will not work on VMK. Apparently it's for collecting 'Kelloggs stamps' if you are logged in with Kelloggs?..I was not logged in.
I continued to play level one and finally reached the end where the treasure chest is. I was given a code that did work on VMK, it gave me "Skeleton at the Helm, Pirate Map Table and Pirate Treasure Chest color brown".
I moved onto level two in the game and was frustrated, wondering if it's even possible to do the level with all the stuff in the water in front of you, just didn't seem like there was a clear path anywhere. Also, was told I was 'hit' when I know for sure I didn't sail into anything in front of me, and was not near the cannons.
So, I thought I'd see what level 3 was like. It moves a little faster than the other levels, but was much easier to get through! I made it to the end, the treasure chest, on (i think) my 2nd try. I have since 'won' a bunch of times on level 3. I used two of the codes that I was given at VMK, (all codes were different, without closing the window) and got the same items that I was given with the code from level one.
I tried using the codes that I had already used with an alternate player of mine on VMK, the code was not recognized. Definitley one time use codes.
I currently have 3 different codes that I have not used, I'm pretty sure I would just get the same items I got with the first 3 codes I did put in.