Spell Completion: This is the activation method for scrolls. A scroll is a spell that is mostly finished. The preparation is done for the caster, so no preparation time is needed beforehand as with normal spellcasting. All that's left to do is perform the finishing parts of the spellcasting (the final gestures, words, and so on). To use a spell completion item safely, a character must be of high enough level in the right class to cast the spell already. If he can't already cast the spell, there's a chance he'll make a mistake. Activating a spell completion item is a standard action (or the spell's casting time, whichever is longer) and provokes attacks of opportunity exactly as casting a spell does.
Spell completion items are items that require a certain amount of spell knowledge to use them without issues.
Under Using Items:
"Spell Completion: This is the activation method for scrolls. A scroll is a spell that is mostly finished. The preparation is done for the caster, so no preparation time is needed beforehand as with normal spellcasting. All that's left to do is perform the finishing parts of the spellcasting (the final gestures, words, and so on). To use a spell completion item safely, a character must be of high enough level in the right class to cast the spell already. If he can't already cast the spell, there's a chance he'll make a mistake. Activating a spell completion item is a standard action (or the spell's casting time, whichever is longer) and provokes attacks of opportunity exactly as casting a spell does."
Monk's robe grants passive bonuses and as such is a use activated item, so the prerequisite can be skipped. DC, as you say, would be 20.
Wings of Flying on the other hand are Command Word activated magic items - while they mimic the Fly spell their prerequisite can still be skipped.
Basically, the "cannot skip prerequisite" only applies to scrolls, wands and potions (out of the items in the book - DM created items may be also be limited).
Basically, the "cannot skip prerequisite" only applies to scrolls, wands and potions (out of the items in the book - DM created items may be also be limited).
As well as staffs, as they are spell-trigger items.
Oh, forgot them.