Here is a list of all the quests that can be completed by a level 3 Skiller. There are a few other quests that are not on this list that may be completed, but I will eventually attempt them and add them if it's possible.
* = Requires rings of recoils and food, but can still be done without help from another account.
* = Requires using Rings of recoil on a 2nd account (1 damage dealt by skiller, 2nd account MUST hit a 0 to gain aggro, then recoil the rest of the damage. If the 2nd account deals any damage other than recoil, it will not count as a kill for the skiller/Level 3.
Biohazard *
Black Knights' Fortress
Client of Kourend
Clock Tower
Cold War
Cook's Assistance
Demon Slayer *
Digsite, The
Doric's Quest
Druidic Ritual
Dwarf Cannon
Eagles' peak
Elemental Workshop I, The *
Enlightened Journey
Ernest the Chicken
Fishing Contest
Gertrude's Cat
Goblin Diplomacy
Golem, The
Hazeel Cult
Jungle Potion
Lost City *
Lost Tribe, The
Misthalin Mystery
Monk's Friend
Murder Mystery
Pirate's Treasure
Plague City
Prince Ali Rescue
Recipe for Disaster (not all parts)
Helping the Cook
Freeing the Mountain Dwarf
Freeing the Goblins
Romeo and Juliet
Rune Mysteries
Sea Slug
Sheep Herder
Sheep Sheerer
Shield of Arrav
Tourist Trap, The *
Tower of Life
Tribal Totem