Dang, dude. Just play the game! You'll find out.
After you complete all the levels, you start over with faster enemies. They continue speeding up with subsequent cycles. If it's still too easy, try playing while your ex-girlfriend throws shoes at you.
Oh, come on. It's not that hard. Just keep playing, and you're bound to get better. Every level is beatable, and every keg (at every speed) is attainable.
Go to your Options screen and clear your high score. This resets your Leaderboard preferences, including your name. It will ask you for your name again after your next game. It doesn't change the name you've already submitted to the Leaderboard, so you'll have to beat your previous high score for your new name to show up. But we both know you can do better.
Yes you can. Don't be lazy. Get in there and do it!
That's not exactly a question, but I think I know what your deal is. You clicked the "Don't send my scores" button, and now you want to undo that. Dang, man! Well, go to your Options page and clear your high score. This resets your Leaderboard preferences.