Szander's page

What is the difference between "Choose one spell that you know...", and "Choose one spell which you have the ability to
cast"?
Does the latter quote refer to a spell on your spell list? Does it refer to a spell known or in your spellbook? I ask this from the perspective of a Sorcerer. If it is the latter then the "Preferred Spell" feat is useless to Sorcerers, Bards and Oracles. If this is the Intent then I am OK with it, I just want a developers clairification.

Is the Gamemastery Guide an official Rul;es source for PFS. My specific interest is in the drunkenness rules, but I am sure there are other pertinent rules that could come in handy.

There is some significant confusion in our group about the disguise skill and it's associated bonuses from magic. In the skill itself it states that these items/spells give a +10 bonus. It specifically references Alter Self in this entry.
Under the Polymorph school entry it states that these spells give a +20 bonus to disguise. The confusion comes from the fact that Alter Self is a Polymorph spell. This has led to the discussion of whether there is a error in the book, and what the real bonus should be.
Has there been clairification by anyone with authority on this subject? I was unable to find any, but my search-fu is not that strong.