For achievements to work, we must not enable sv_cheats. That's why I included commands that work without sv_cheats to help you pass all the trials if it's too difficult for you and to save some time (you still have to pass every trial on all maps).
For Least Damage, Least Bullets, and Least Kills, we need the enemies not to resist, so with the command ai_disable we disable the AI and just walk around the enemies without shooting or killing them.
For Least Time tests we need to move quickly, with the command ent_teleport player we teleport to where our aim is directed, and may get stuck in the textures, so save before teleporting.
For Most Mass tests we need to swallow heavy objects, and one of the heaviest and most comfortable objects is our transport, it weighs 3000kg, you can save it with the command ch_createdrivableapc.

• Go to Keyboard Settings, scroll to the bottom, and turn on the Developer Console.

• Press ~

• Enter the three commands one at a time
  bind "1" "ai_disable"
  bind "2" "ch_createdrivableapc"
  bind "3" "ent_teleport player"

By pressing keys 1, 2 and 3 you activate the commands you need (you can replace them with the ones you like).