Spoiling is not allowed under any circumstances. Spoiling is any instance in which a user asks for or gives out any information regarding quests or what eggs hatch into which Pokémon; this also includes telling users how to enter the PF chat.
Saying that an item is for a quest is allowed (when it actually is for a quest; saying it is when it isn't is not allowed). Saying what quest it is for is not.
Note that this rule includes the use of off-site guides. Most of them are wrong and will cause the System to flag your account if you follow their instructions!
No one is listening.