Solve your first puzzle
Kill the first zombie on the first try
Have the rope set before you enter floor m1
Do not have the rope set when you enter floor m1
Reach m1 floor
Cut off lab lead's finger before you actually need to
Have the hazmat suit and flashlight on you when you approach the chem storage room for the first time
Check the inventory catalogue before you go for the welding metals
Kill all zombies without taking any damage
Restore the gates
Reach the security office on 1st floor and start watching the cams' footage