Just want to make sure I have this right.
There doesn't seem to be a general rule on spell completion items I can find.
Specific types of items list requirements to use them.
Multiclass dedications don't seem to have the playtest language limiting spellcasting items to a level you can cast.
The only item I've found said limits on are staffs.
So wands and scrolls can be used by anyone with that spell on the list of their tradition.
So any divine caster, including someone who just took the cleric dedication, can use a scroll or wand of Heal. But you can only cast non-cantrip spells from a Staff of Healing if you can cast that level of spell.
How am I doing?
Gonna bump this too.
You seem to be correct. It just seems to require you to be able to use the Cast a Spell activation, which requires you to be able to use the Cast a Spell activity, and have a Spellcasting class feature, which casting classes obviously have and the archetype section specifically prevents any ambiguity for Multiclassing, though classes like Champions or Monks or Rogues with Minor Magic, even though they have a magical tradition and can use the Cast a Spell activity, can't use Cast a Spell activations, because they don't have a spellcasting class feature. But otherwise, no level requirements that I can see.