How does undead anatomy work?

Here is the description of the undead anatomy spell: Undead Anatomy

Here are the general rules about polymorph spells.

There are two points that are contradictory in these rules:

  1. Which natural attacks do you obtain?

    • The spell says you get a bite attack and two claw/slam attacks, but what if you polymorph into something that has no mouth, do you still get the bite attack?
    • The generic text says you get the natural attacks of the creature you polymorph into, do you cumulate these with the bite+claws of the spell? (it sounds silly)
  2. What exactly are the creatures you can polymorph into?

    General rules say you can’t polymorph into a creature with a template, but the spell suggests as an example that you can polymorph into a zombie or a skeleton, without clearly indicating that it is an exception to the general rule.

    Can you polymorph into other simple templates such as a human-vampire or an elf-lich? Can you only use the archetypes that make a creature undead so you can be a gorilla-mummy but not a bodak-clockwork? In this case can you be a dwarf-zombie-lich?