Hello Shadree. Thanks for the feedback.
-I've taken your advice and now mention the stab mechanic in description.
-To my knowledge, enemies can't see through walls. I've never encountered this. The red visor juggernaut has special vision, though, so he can see you even if he is walking away from you.
-The red key is used on the red door.
-If you run out of c4, or if you have no more enemy bodies to activate the special door switch, you may have to restart the level(by dying or by pressing escape to go to menu)
-The only way to dodge bullets is to run away from them. There is no jumping in this game.
-It takes 1.3 seconds of standing on the elevator buttons to activate the elevator. Please note that if the elevator is already in motion you will have to wait until it stops to activate it again.
One thing to note is that the grayish door can only be opened by an enemy(or an enemy corpse).