Hello,

I just finished SS1 and had a lot of fun (again) :)
I played that game 20 years ago and couldn't remember much. But I thing I could remember: On the maintenance level I had to find someones head in order to open a door that had to be unlocked using a iris scanner.
But this time this sub-mission was missing. That door was always locked and I was never asked to open it. How does it come?

I'm pretty sure you're never asked to open it, it's just there and if you don't vaporize the head like I did (d'oh), opening it is a thing you can do.

its actualy depends on what you set the story difficulty to. think that the iris scanner is only needed on story difficulty 3 but not 100% sure

You will also need to get the level security to (near) 0% (the difficulty level may affect this). There's a button / lock blocked by Shodan before the retinal scanner. It is there, I've just played trough again =)

You need to be in a later stage of the game to be able to destroy all cameras on the level.