There are only one pre-game Booster in AlphaBetty, the King Crowns.
The plan was to have three, but the second and third pre-game Booster were never introduced, so therefore the buttons are still there showing a padlock.
Yes, My computer will only let me play up to on 410. But my android tablet and again android phone I could go to further levels. I think it is cause I was playing through an ap. I'm not sure though a question for the administration?