Question:

For the achievements that require full playthroughs, especially Ghost and Clean Hands, am I able to complete missions in any order under these conditions?

Suppose I played Missions 2-5, then 7-9 fulfilling the conditions (no alerts, no deaths), then I go back and complete Mission 6 with the same conditions. Will I be awarded the achievement following completion of Mission 6? Or does the game require an entirely "New Game" selected from the menu screen?

Thanks! Couldn't find the answer anywhere online, sorry if this is a repost.

Select "Return to the Tower - Mission" (or something like that) from the load menu and complete the story from there.

I think what he's asking is if you need to complete all levels with these requirements (Not killing anyone or not being detected) in a single playthrough, or if, say, you didn't kill anyone or get detected in level 3 on one playthrough, and you play 1, 2, and 4-9 on another playthrough with getting killed or detected, would you get the achievements?

I'd like to know as well.

I think it is one playthrough. Just note: and I think you can't kill weepers either. I did both and got the achievement.