Gears of War ONE question

My first play through is going to be in insane mode cause I'm playing co-op with a friend. When I beat the game, will I get the achievement for hardcore and casual as well?

I too can confirm that you get the achievements.

Yes, you will get the achievements for the lower difficulty levels as well... I remember when playing it me and my friend started on hard and we got all the other achievements for the other difficulty's as well... Kudos!