Updated Walkthrough, with new Item additions and some Fat guy changes!
Mission 1
Your only "goal" is to reach the Beacon, you can do it right away and end the Mission. But the entire point of the mission is to get points and unlock gear.
The trick is to focus on killing Zombies and Dogs for time and loot, and only shooting the targets for points inbetween that.
First focus should be unlocking the shotgun (from start first branch right). With the shotgun, you can easily dispatch fat guys. Until then, you have to find a route that doesn't run into them.
Targets give more points when you hit the red pieces or spots. There is a whole bunch of cubes in the room before the exit.
Important note: You have to end the mission with an unlocking score to unlock gear. You do not have to pick up the gear.
Dying to the timer does not count as ending the mission, you have to touch the exit beacon!
Gear you previously unlocked remains unlocked when you restart the mission, even if it still has a "score pricetag".
Mission 2
Grab 2 Plates from left and right path branches, insert them to circuit box next to the locked door, pass through.
Sewer key is on a pallet next to the wall to the right when entering.
[Area contains Rifle, a hand grenade, shotgun ammo.]
Unlock door, climb, approach room exit to trigger 3 minute arena.
You can totally mow down all of the Zombies if you can score headshots - they drop ammo after all.
Just be careful, combat loot disappears after a short while.
Otherwise, just move in a circle around the room, vault the obstacles, they can't really keep up with you.
[Fun fact: If you kill all Zombies quickly, you still have to wait for the Timer. Flashbang after door.]
Climb up into open area. Press M to enable a target beacon for the mansion.
[Shortcut to mansion: From taking control, turn left and follow the path. When out into the open, turn about 20 degrees right.
Run towards the tree in the distance until you see two trees to the right.
Run towards those. Beware the dog. Next to the two trees, on the left, there is an opening in the rock wall.
Run through that and you are straight infront of the gate.]
Mansion gate is locked, Zombies right next to the brick walls drop it. You can use the gate to make him come running, too. (Left corner when looking at gate towards mansion)
Mansion front door is blocked by cabinet, go to the side and push to clear. Key for front door is on a shelf all the way to the left on the porch.
[Shotgun on right side end of porch]
Now inside mansion. Meet first fat guy in the back left. If you are clothed, he will do an inescapable but dodgable charge attack that strips you. If you dodge he will just charge again.
Just stay stripped and he won't do the charge attack.
[You don't have to trigger him until all the way to opening the Diamond door. Just stay out of his vision cone]
[[Or: Two hand grenades on table to the right. Use them and the shotgun to MURDER THE CRAP OUT OF HIM. Shotgun ammo near the middle door]]
The goal is to collect 4 plates and put them into the machine on the wall to the right. There is several doors and paths, but since they are locked by subsequent keys (heart, club, spade, diamond) it's fairly linear.
When entering the Main Hall, take the door to the right. There is one open door, a filing room of sorts, find the Club Key inside.
[Rocket Launcher and Flashbang in Filing room. Note: I havent seen AMMO for the dumb thing here.]
Back to Main Hall, now the door straight: Leads to heart door and a stairwell to second level. Heart key is on a cabinet on second level. Plate and key in heart room.
The second level door takes the Club key. Find Spade key in the room inside.
Exit back to main hall. Use first door again. At the end of a long hall the door for the Spade key you found. [Incendiary grenade here] Stairwell to level two, follow it to get to main hall second floor.
You have to push some cabinets to get at stuff under them. Hall half-hidden behind shelf opposite to your entrance point. Plate in cabinet, next key near the end of the halfhidden hall.
Beware fat guy. [OR MURDER HIM. Grenade, Inc. Grenade, (2)Shotgun and rifle ammo on second level.]
Last key - diamond - opens door from ground floor main hall, left side. Final plate through there. Put all plates in machine and touch the green crystal (beacon) to "end the mission".
[Fun fact: Using grenades you can achieve more than 100% accuracy]
Mission 3
Go to mansion. Front gate is unlocked, front door key is on the inside of the front gate. Fat guy in garden, but hes juuust out of range of the front gate. You can sneak past if you hug an inner wall past his vision cone.
Basically re-do a mansion run except the plates and keys have slightly shifted positions. [Shotgun left of entrance in main hall, ammo in main hall]
Notes: Heart key is in the open near the heart door. One plate is now half-hiding behind a shelf on the main hall second floor. Diamond key in cabinet on second floor foyer. Diamond door is optional, there is no plate inside.
[Fat guy on second floor can be avoided entirely. Rocket launcher near the last 2 plates on second floor. Rocket and Inc. grenade in Diamond Room]
Once all plates are placed, exit the mansion and go back to the sewer grate. Enter.
As you backtrack the sewer, kill all enemies because they drop a plate for the breaker box and the sewer key.
The second plate is stuck to the ceiling near the green goal shoot near it to get it. The third plate is in the room with the dogs, "islands and bridges", on a barrel. In mission 1 there was ammo in that spot. The final plate is at the Mission 1 spawning point.
The breaker box is on the wall in the room with the dogs and "islands with bridges", basically the first big room from Mission 1, opposite of the ladder. Return to goal in the arena room and touch it to finish this version.
Mission 4
Goal is to kill all enemies, then touch the beacon. Right at the spawn there is a Zombie on a roof you cannot get to. Shoot it from the street.
Otherwise just sweep and kill. Some enemies stand in dark corners. Several are inside containers or out of level bounds.
There is a ladder to a roof area later in the level. On the roof area, there is a kind of mesh blocking the path, Zombie dog on roof behind it.
There is a Zombie all the way in a dark corner on that roof impossible to see, FYI.
[There is a rocket and Rifle ammo here, but neither of those weapons.]
Mission 5
Disclaimer: This level is super tedious and you dont want to play it.
Seriously, it takes like 45 minutes if you dont waste time.
You have to free 3 crystal light beams onto the crytal over the Beacon to finish.
One of the light crystals it at the bottom of an elevator and needs to get driven topside first.
The elevator requires 3 fuses to operate. 2 of them are fairly close the the Beacon, one is not.
There is no loops in the level, its all dead-ends and a couple branches, so do what any rational explorer would do and just hug a wall.
Hug the left, because if you hug the right you will have to re-do parts of the level.
You should find the first fuse on a crate before encountering the cave with the sewing machine and the Beacon.
Continue hugging the left and just run down the entire cave. Dont die, you will have to do-over everything except collecting fuses.
The second fuse you should encounter is far away from the Beacon, next to a shaft collapse.
You will run into crystals and their beams. Where the beams seem to stop midair, theres invisible shit blocking them.
Just shoot to make them visible, shoot some more until the beam passes.
Repeat until the beam reaches the Beacon, but dont deviate from hugging the left wall or you might get lost.
You should have freed 2 beams and have 2 fuses by the time you move towards the elevator area.
The third fuse is randomly on a crate not too far from the Beacon, where the crystals for the third beam are present.
Run it down hugging left all the way. You will see the top of the elevator first and what feels like hours later arrive at the bottom of it.
At the bottom of the elevator there is a crystal beam too, but it ends with an overturned crystal, dont bother with it.
Use the fuses and let the elevator ascend. Run back to where the third fuse was (hug the right now if you dont want to bother thinking)
and unlock the final beam.
Finally, here's my updated save (Apr 13th 2021)
Should work with BioasshardRelease0 4 254-Rev1
Fox Release, with extra ammo and extra crit cards
All weapons unlocked
All clothes unlocked