Bioshock Hardmode

Small question, does anybody know if you can get the Seriously Good At This achivement(Everywhere says ‘Complete the game on the hardest diffculty setting’.) for Bioshock if you started at the Normal difficulty but then switched to Hard Mode in mid game?

i don’t know but when i was playing i started on hard and then i switched to medium for like a minute because my friend was playing and then switched back and when i beat it i didn’t get the achievement

Nah. You have to play it all the way through.
My friend and me played it like that, and it worked, but when we
switched it, it didn’t.