Duke Nukem Forever Puzzle

This puzzle is for Duke Nukem Forever, it lasts for a week. Hopefully you shouldn't find it too difficult to solve.

If you already have the game then you can still try solving the puzzle as the giveaway has links to the "The Doctor Who
Cloned Me" and "Hail to the Icons Parody Pack" DLC's.

Giveaway format is http://www.steamgifts.com/giveaway/xxXxX/

All questions have something to do with the game.

1) Execute 20 aliens (Second letter of the third word)
2) New weapon found in the single player DLC (Second letter)
3) None of the multiplayer levels (including DLC levels) have this letter in their name
4) 14 of the 23 single player levels contain this letter
5) Last level (First letter)

Please don't post the answers.