Hyrule Warriors definitive edition all challenge types explained a little bit (Master Quest Map)
Don't get hit- One hit on you and you're dead. The enemies don't get the same treatment... The hard worker skill on your fairies will help revive you if you mess up (only once and you won't get as much health as before).
Speed Run- Clear the battle in 20 minutes. 14:59 or less is still your A rank requirement but clear the stage faster if you are a perfectionist.
No item attacks- Can't use bombs, bow, boomerang, hookshot, or hammer at any time in the battle. This will make giant bosses harder to defeat because it's required for weak point smashes. You'll have to use focus spirit.
No healing- This means no health potions can be used in battle and no hearts will be found to heal you. This is really no problem if you know what you're doing.
No guarding- just like the title said guarding will have no effect on the enemy. Personally it does nothing to me because I don't have time to guard by the time the enemy is dead sooooo, not a problem at all.
