Are you supposed to be able to beat LIMBO without dying?
LIMBO is a game of trial and error, it is expected of you to die until you "solve" some of the levels.
While some levels give hints where danger awaits, it'll rarely straightaway tell you "if you step here you'll die", these will only serve in retrospect, letting you know what gives away what killed you last time, allowing you to prepare better for your next try.
The achievement/trophy for completing the game without dying is aimed for players playing through the game a second time, encouraging them to memorize the stages.