I have no idea what you guys are talking about. I can use higher level medical supplies in place of lower ones no problem. Just click the empty square to go to your inventory and click a higher level supply. Also,a, great place to get grade 3 items is by recycling medical kits.
Grenade Achievements - Equip melee weapons. Keep a player in the green zone. (Players in the green zone will not automatically pursue zombies.) Use another player to run around and herd the zombies to the player in the green zone. That player throws a grenade! (It might be easiest to herd zombies by going to a lower level and using a non-scavenging player to scavenge.)
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