Q16: If a psicrystal takes the Wild or Hidden Talent feat, it can hold a focus. Can you use your psicrystal's focus for metapsionics without Psicrystal Containment?
No. Psycrystal Containment is a specific exception to using another creatures focus.
Q16b:If the psicrystal takes the Wild/Hidden Talent feat anyway, can the owner use the psionic focus even if the psicrystal focused itself, rather than having the owner spend a full-round action focusing it? I assume the focus it gains via Psicrystal Containment is functionally the same, preventing it from being double-focused or something.
Only if you house rule you can use a cohort or other person's psionic focus.
Isn't that what Psicrystal Containment does?
Psicrystal containment allows you to store your own psionic focus in a psicrystal as a spare, it doesn't allow you to use it's psionic focus.
OK so there's a detail here, that might not have come up before (idk / iirc).
The psicrystal could use the Focus, that the Psion placed into it.
The psicrystal (normally) can't Focus itself.
The psicrystal (normally) hasn't any way to use the Focus itself, after the Psion puts the Focus into the Psicrystal.
but IF ...
The psicrystal has Wild Talent for the psionic subtype and [Host] feat for a power and an ML
or Hidden Talent and something else to get the ML,
it would be able to use the Psion's Focus, that the psion put into the psicrystal,
on whatever power the Psicrystal has
itself , on it's own.
The psicrystal could get Psi Focus on it's own,
if it could get a Constitution score. That takes time.
Undead get to use Charisma to get psi-focus (iirc).
Undead + Psicrystal = I have no idea.
The dreamscarred guys may have used a houserule like this.