Monster with Automatic Defeat

[Pandorino]

HI all :) my question is about monsters with automatic defeat against item /ecc
for example : "fire/flame attacks defeat automatically this monster"

If i'm level 9 , open door , and find one of these monsters ( for example fire/flame ) and i have one item fire/flame :

- i win directly ?
- other players can use "wandering monster" and i fight with this monster ?
- other player can use a curse to eliminate my fire/flame item ? monster is already defeat ?

thanks