How broadly do "classes" from Mystical Theurge & Magical Knack apply?

[Marcella]

I started a cleric but have no experience with spellcasters in PF. To my untrained eye, getting the Magical Knack trait & dipping into an arcane class for one level to then go Mystical Theurge looks like a good deal. Is it? (If it matters, I'm in PFS and thus won't progress farther than 11th level. And, part of my motivation is to just try out the various arcane spells.)

Specifically, do the levels gained from MT apply to:

1) Spells that wizards learn with each new level? (An FAQ at http://www.d20pfsrd.com/classes/prestige-classes/core-rulebook/mystic-theur ge says "no".)

2) Cleric domain powers that they get at certain levels? (E.g. acid resistance at 6th cleric level of the Earth domain.)

3) Spells from a cleric domain and their potency? (E.g. getting "spike stones" at 4th level that then last 1 hour per cleric level)

4) The two previous questions for wizard schools & sorcerer bloodlines?

5) Level-based benefits to a wizard's familiar?

6) "Channel energy" and other feats gained via a component class's levels? (I assume "no".)

And what about the +2 "trait bonus" to caster level that can be gained from Magical Knack?

References:

"Magical Knack: Pick a class when you gain this trait—your caster level in that class gains a +2 trait bonus as long as this bonus doesn't raise your caster level above your current Hit Dice."

and

"When a new mystic theurge level is gained, the character gains new spells per day as if he had also gained a level in any one arcane spellcasting class he belonged to before he added the prestige class and any one divine spellcasting class he belonged to previously. He does not, however, gain other benefits a character of that class would have gained. This essentially means that he adds the level of mystic theurge to the level of whatever other arcane spellcasting class and divine spellcasting class the character has, then determines spells per day, spells known, and caster level accordingly."

[jbadams]

Magical Knack increases your caster level but does not grant higher level spells known, so it wouldn't help you to qualify for Mystic Theurge.

Mystic Theurge grants additional spells per day, spells known, and increased caster level; you don't gain anything that isn't one of those.

[Chess Pwn]

1) Correct you'd gain no spells
2) No, your domains wont progress at all
3) You gain cleric domain spells when you can cast spells of that level and they are done at your total cleric caster level, which is your cleric level plus the boosts to it from MT.
4) wizards and sorcerers have nothing that progresses
5) familiar doesn't get any level based bonuses, just the bonuses from your stat increases.
6) Correct, it's a no.

Now these answers probably matter less now since you can't get in sooner than lv7 since that trait doesn't do what you think it does.

[My Self]

Just as a tip for PFS, stay out of Mystic Theurge as a first-time build. Minimum level to get in is 7, because you need 2 spell levels from a divine and an arcane class. Since caster levels don't advance spell levels on their own, at its fastest, it works out as:

Wizard or Witch 1 (SL 1)
Wizard or Witch 2 (SL 1)
Wizard or Witch 3 (SL 2)
Cleric, Druid, or Shaman 1 (SL 1)
Cleric, Druid, or Shaman 2 (SL 1)
Cleric, Druid, or Shaman 3 (SL 2)
Mystic Theurge 1 (SL 2)

Consider that these Cleric or Druid levels will occupy a quarter of your PFS life, and that for half of your PFS life, you won't cast higher than 2nd level spells. To contrast:

Wizard/Witch/Cleric/Druid/Shaman 1 (SL 1)
Wizard/Witch/Cleric/Druid/Shaman 2 (SL 1)
Wizard/Witch/Cleric/Druid/Shaman 3 (SL 2)
Wizard/Witch/Cleric/Druid/Shaman 4 (SL 2)
Wizard/Witch/Cleric/Druid/Shaman 5 (SL 3)
Wizard/Witch/Cleric/Druid/Shaman 6 (SL 3)
Wizard/Witch/Cleric/Druid/Shaman 7 (SL 4)

As a single-class full caster, you could be 2 spell levels higher than a mystic theurge. That's the difference between Invisibility and Greater Invisibility, or between having no Haste/Blessing of Fervor and having your Haste/Blessing of Fervor. Also compare:

Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 1 (SL 1)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 2 (SL 1)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 3 (SL 1)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 4 (SL 2)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 5 (SL 2)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 6 (SL 2)
Bard/Inquisitor/Magus/Summoner/Hunter/Warpriest/Skald 7 (SL 3)

After 4th level, you will be casting worse than a 2/3 caster. Your whole deal is casting, and you'll be casting lower-level spells and probably also fewer of them than people who do other things besides cast. This is not good. You barely reach the same spell level as a 2/3 caster at level 10, and you're still 1.5 spell levels behind a full wizard or cleric: you only get 9th level spells at level 20, which is 3 levels late. And you only get that for 1 of your caster classes. You'll almost certainly need multiple caster stats if you want to have 9th level spells at all, ever.

Anyways, to make this shorter, don't kill yourself and your party as a Mystic Theurge. The concept is amazing but the prerequisites are horrible. I'd recommend you ease yourself into becoming a caster by playing an Inquisitor or Bard or something that has a non-casting option.

[Dasrak]

Mystic Theurge is a perfect example of something that looks awesome on paper, but is horrible in practice. Magical Knack alleviates their problems, but it's not nearly enough to solve the issues.

I'd avoid Mystic Theurge entirely in PFS. It only really shines at higher levels (like 10+) so for most of your career you're just gimped, and the one place where it really excels happens to be raising undead minions. It's just really terrible to begin with and on top of that the PFS format is unkind to it. I really can't recommend it to anyone under those circumstances, as cool as its concept may be.

[My Self]

Also, you won't be tossing around as powerful things as, say, a single-class caster. At best, you'll be a spell level behind and -1 on your DCs, sometimes you'll be two levels back and -2 on your DCs. If the prerequisites cost you less, or you got a lot more of that (16th level minimum) spell synthesis, it might be worth it. Even then, you won't shine in a party with a dedicated arcane caster and dedicated divine caster.

Play a regular full caster.

[Dragonchess Player]

One "non-horrible" mystic theurge for PFS is magus 6 (to qualify for Broad Study)/cleric (negative energy) 3/mystic theurge 3+. The cleric buffs and spontaneous inflict spells can help out the magus' spell selection and staying power.

Otherwise, the "classic" (two 9-level caster classes) mystic theurge can work as a "support caster" in PFS: concentrating on buffs and utility, with some limited (i.e., no save) battlefield control.