Immunities, Vulnerabilities, and Polymorphing

[i208]

I have a very specific question/circumstance regarding polymorph spells and how they relate to energy immunities and vulnerabilities in two parts:

If a character/creature which already has Fire Immunity and Cold Vulnerability casts Form of the Giant I to become a Frost Giant... 1) Does it retain Fire Immunity or does the vulnerability gained reduce the immunity. 2) Does the Cold resistance 20 gained apply first then the cold vulnerability or the vulnerability then the resistance, or do they all change based on a chart somewhere?

Essentially how do inherent energy tolerances affect those gained from spellcasting?

Thank you in advance for your input. If this question has already been asked in a prior thread I apologize I did not find it amongst the myriad of Polymorph Spell threads. They raise a lot of questions and for the moment I just need the answer to this one.

[Lorathorn]

I'm no expert, but I think it depends on a few things. Is the Fire Immunity/Cold Vulnerability innate somehow? If so, I'd say that the polymorph to a Frost Giant would probably supersede both of the prior effects. I think polymorph even further specifies the losing and gaining of supernatural and extraordinary abilities, which would include those innate bonuses.

If you change form into something that has a vulnerability, you would gain that (assuming that the spell specifies it). Then, if you had some manner of spell based energy resistance, it would resist the energy, but not remove the vulnerability. Thus, any spillover damage would be increased accordingly (I assume this is the order of operations).

But ultimately, it would seem that polymorph would override any innate immunity or vulnerability, regardless of the new form. The act of polymorphing into some animal with no such defenses or vulnerabilities would remove any innate energy defenses or vulnerabilities enjoyed by the spell's recipient.

Sheesh, why does this seem like legalese all of a sudden?