Mnemonic
Let's start out in style! This one will give you more proof of the fact that Agent 47 is not just anybody who wields some far-out gadgets. He is a born assassin, with just a natural need to express his essence. What is his essence made up of? A cold mind, of course. And what happens when we put it to a test? Pretty much the same thing that happens under any other circumstance whatsoever.
While making your way into the level, take the stairs in front of you and make sure to reach the left side of the building on the left side of the street. You will find a ladder letting you in, and no sooner do you step in than you will be given an opportunity to take the disguise of a block guard.
While making your way up to the top of the building, you will need to open the door on the right using the code panel. The code is 2552. At the top, just behind the target on his right side, you will find a test subject standing in the bathroom, so you can discreetly take his outfit.
Wait for Hush to go to the other room, then proceed to kick out the female worker watching over the operations and hide the body behind the whiteboard. Hush will be coming back with a new female worker and will dismiss the previous test subject. Sit comfortably down in the chair and measure yourself up against him, resisting when needed.
Just a casual way to show off the material you're made of, wouldn't you agree? It serves Hush right for performing such experiments on homeless people as well.
Deprivation
This one will have you starting the level in pretty much the same way as the Mnemonic challenge. The only difference being the fact that you will need to take down Hush while he is sitting in a chair in a different room from the one you will be operating in. So, while at the top of the building, in a block guard disguise, go across the room and take the other set of stairs down, to the first lower floor. Take the poison from the desk the scientists will be found working on.
Still one floor lower than the one you took the lethal poison from, reach the other side of the gate which will stand in front of you as you are making your way down, to take the fuse. Back in the experiments room, two floors up, find Hush's room on the right side and place the fuse in the fuse box, near the worker.
Wait for Hush to sit comfortably in the chair back in his room you placed the fuse cell in and when he is there, you will have at your disposal any method to take him down to complete the challenge. A gunshot is, of course, the most efficient one, but if you prefer to use the poison, that will take you across the finish line as well. So, place the poison in the vent found just outside of the experiment room and eliminate Hush from a distance. The challenge can be completed only if he dies near the chair though.
Bullet Points
This one will let you take down both targets with a single shot fired from a sniper rifle. Not bad. It does require some finesse on your part, however.
First things first, after taking the set of stairs on the left side and going through the “Wet cat laundromat” building put the code 0118 in the panel to open the back door. Going up, on the first floor you will find a wrench and on the balcony, two men will be talking, exposing the “All-seeing eyes” mission you would do well to follow through.
So the broken drone you need to scan with your camera is found at the top of the building. After that, you will get the information that you are required to take down several other drones with a sniper rifle in order to make for an angry meeting of two targets. While still on the outside, make our way down to reach the next-to-the-top level and take out the guard to pick the sniper rifle he is taking care of.
Having returned to your vantage point, destroy other drones. They will be moving through the air, though, and this will be the hardest point in the mission. Study their movements and fire the shots both slightly above and slightly before the point they are close to reaching in their projected trajectory. That way, you will not be wasting unnecessary ammunitions, which in any case are not infinite. Use them wisely, only when you are sure to hit the target. It is also advisable to save the game just as you are about to shoot, for this part of the level will most likely require you to repeat it a couple of times.
Now, having taken down the required drones, Royce will be furious over it as she will be thinking it's all Hush's fault. She will make for the launch of the two additional drones near the Hush's penthouse, only to be promptly taken down on your will. They are going to be travelling in the air on the left-hand side. As she storms to a fiery meeting with Hush, she will be completely exposing both of them to your mercy. Watch out for the guard that will reach your back before you proceed to fire a deadly shot.
If you prefer to complete the Big Bada Boom challenge, instead of firing a bullet that will go through the bodies of both of your targets, just aim for the gas container close to Royce, using the instinct vision to locate it precisely.
A Shock to the System
ICA data center will be your point of entry to this challenge. To reach its facility, take the first two sets of stairs, then take the one on the right. At the end of the path, you can go up by taking another set of stairs, but you will be required to listen to a woman talk to herself, while she is trying to remember the entry code into the facility. Take her down then if you prefer and put the code into the panel standing on the yellow container, on the very ground level. In case you missed the code, it is 0118. And that is how you enter a secret organization facility!
As you are going on the right of the staircase, make sure to step over the rails on the edge of the corridor, near the door to reach the level below. The break room and the server room B-02 are next to reach, and they are located just at the point where you dropped down from the rail. You will find it indicated on the wall anyway. As you hack the break room's glass panel with your camera and turn on the air conditioner, first a woman and then a man will come your way to investigate the distraction. Use the server room B-02 to hide the bodies. The third time you repeat the process of turning on the air conditioner will make the guard to investigate the break room, so be sure to knock him out and take his disguise which will let you reach the working stations unharmed.
Once you hack a handful of these, you will dismiss the personnel on a break, so make sure to step into the guarded room just in front of the working stations and pick the screwdriver. Now you have everything you need to complete the challenge. Royce will be making her way as well into the break room, so when all the personnel abandons it, expose the wire from the plug and create a leak from the watercooler, then move away promptly from it as it will then create an electric puddle of water right on the place where Royce is standing.
Medium Rare
Once inside the ICA facility (see the Shock to the system challenge above), go over to the server room A-01 and hack the vent panel inside with your camera. Just as you are on the other side of it, make sure to bring the screwdriver that's on your left, before proceeding. By sneaking your way through the corridor and passing through the door on the right at the end of it you will eventually reach a vetting room that hides the dongle you need.
So open the door with the camera, sneak the dongle out as you go back to reach the analysis office door on the right. Passing through it, take right and then scan the vent panel open on the left so as to reach the vent shaft. There is a screwdriver inside it that you can pick in case you missed the previous one, so go over to the far left side of the vent corridor and open the panel. That will let you reach the west side server room a guard will be walking in, so distract him and take his outfit. The panel on the right inside the west side server room will let you reach Royce's control room.
Now from the panel on the left in the room, you will have such power as to fire the personnel. You will need to fire all of them, though the order in which you do it plays the key role here. First things first, make sure to have turned on the frosted glass, as it will impede the guards from seeing what is happening on the inside. Using the panel, Jeremy Bolt is the first to be fired, and Alicia Reynolds the second. As Royce is making her way into the room, make sure to hide back into the panel you used to reach the room. When she leaves, keep an eye on her using the panel to track her movements down as she's reaching the core. Once she is there, proceed to fire Sharon Reed. That will do.
Cooling Down
Repeat essentially the same process as in the Medium rare challenge (see the challenge above) up to the point when you take the guard's disguise. Go back through the vent you used to reach the guard and go back to X.Ming's office, the other end of which will let you proceed and get to the security room. The armory in the middle of it on the left side is hiding a tier 3 dongle, so be sure to pick it up there.
As you are making your way down to the data core, wait for Royce to reach it. She will be resting on the edge of the rail after working on the panel, so take her down by pushing her over into the cooling liquid. And that is how you complete this challenge.