Q132 Psion 20 with Leadership and a Fiend of Possesion cohort. Can the Psicrystal take over physical action, the Fiend of Possesion control his own mental actions and the psion take his own mental actions? Or does the FoP's action overtake the psions?
I think this needs a bit more explanation... I assume you mean that the Fiend of Possession is currently possessing the psion, and the psion has manifest both Control Body and Solicit Psicrystal?
If so... I don't think so. If the FoP is possessing the psion, then the psion can't take any actions, mental or otherwise. The FoP could possess a piece of his equipment instead, though... If the FoP can relinquish control temporarily to the psion, then the psion could take mental actions, but I assume this would require some kind of action on the FoP's part (I forget how that works...).
Q133: if something is polymorphed to another type, can it then be healed by means that would not normally affect it? for instance, a psicrystal, metamorphed to an orc, would a cure spell affect it then?
Yes, since Polymorph changes your type.