A. Context is everything.
A Cleric or Druid can Spontaneously sacrifice a Prepared Spell for Cure/SNA, however, this only applies for that Class's Spellcasting and no other. A Wizard/Cleric/Theurge cannot sacrifice Wizard Spells to cast Cure Minor Wounds. This is backed by practical application world wide and the FAQ.
Likewise, Wizard granted Spellcasting is not Spontaneous Spellcaster. A Domain Wizard with Domain Spontaneity or w/e whom can choose to cast some spells using Prepared Spell Slots is meeting requirements as an End Result, like a Wizard UMDing a Runestaff or using a Ring of Spellstoring. They are still using Prepared Spells in a Prepared Spell Slot, their is no printed exception to their base rules on Metamagic, they are still a Prepared Spellcasting Class using Prepared Spellcaster Rules. Again, backed up in the FAQ.
So no, Versatile Spellcaster which is Spontaneous Spellcaster based, printed in a Sorcerer focused book, and exemplifies Sorcerer, shouldn't be applicable to Wizard based spellcasting which doesn't meet the requirements.
B. Immediately after seeing this, someone will jump in here and mention "RAW" a few times and tell you the FAQ sucks. But they won't offer any real counter points to anything I've said, they are just here to bitch about what they dub a 'nerf'. Their baggage, your problem.