Hi, just trying to shed some light here. These quotes are taken from http://paizo.com/paizo/faq/v5748nruor1fm#v5748eaic9r95, and some of them are relatively new.
- first,
Spell-Like Abilities, Casting, and Prerequisites: Does a creature with a spell-like ability count as being able to cast that spell for the purpose of prerequisites or requirements?
Yes.
For example, the Dimensional Agility feat (Ultimate Combat) has "ability to use the abundant step class feature or cast dimension door" as a prerequisite; a barghest has dimension door as a spell-like ability, so the barghest meets the "able to cast dimension door prerequisite for that feat.
Edit 7/12/13: The design team is aware that the above answer means that certain races can gain access to some spellcaster prestige classes earlier than the default minimum (character level 6). Given that prestige classes are usually a sub-optimal character choice (especially for spellcasters), the design team is allowing this FAQ ruling for prestige classes. If there is in-play evidence that this ruling is creating characters that are too powerful, the design team may revisit whether or not to allow spell-like abilities to count for prestige class requirements.
—Pathfinder Design Team, 06/06/13
- second,
Spell-Like Abilities: How do I know whether a spell-like ability is arcane or divine?
The universal monster rules for spell-like abilities states: "Some spell-like abilities duplicate spells that work differently when cast by characters of different classes. A monster's spell-like abilities are presumed to be the sorcerer/wizard versions. If the spell in question is not a sorcerer/wizard spell, then default to cleric, druid, bard, paladin, and ranger, in that order."
For spell-like abilities gained from a creature's race or type (including PC races), the same rule should apply: the creature's spell-like abilities are presumed to be the sorcerer/wizard versions. If the spell in question is not a sorcerer/wizard spell, then default to cleric, druid, bard, paladin, and ranger, in that order.
For spell-like abiities gained from a class, use the spell type (arcane or divine) of that class to determine whether the spell-like ability is arcane or divine. If the class doesn't cast spells, use the above rule for spell-like abilities from race or type.
Edit 7/15/13: Wording changed match the precedent in the universal monster rules for spell-like abilities.
Edit 9/23/13: Wording updated to clarify racial/type SLAs vs. class SLAs.
—Pathfinder Design Team, 07/09/13
- third,
Prestige Class Requirements: If a prestige class requires 5 ranks in a skill and I have 6 ranks in that skill, do I still meet the requirements?
Yes, because skill ranks are inclusive: if you have 6 ranks in a skill, then you have 5 ranks in that skill, and therefore meet the "have 5 ranks in [this] skill" requirement.
In the same way, if you have a BAB of +6, then you have a BAB of +5, and therefore meet the "have BAB +5" requirement.
In the same way, if you have Str 15, then you have Str 13, and therefore meet the "Str 13" feat prerequisite for Power Attack.
However, spellcasting ability is not inclusive: it is possible (mainly through the use of spell-like abilities) to be able to cast 3rd-level spells but not 2nd-level spells. If you can only cast 3rd-level spells, that does not meet the requirement of "able to cast 2nd-level spells."
Likewise, feat prerequisites are not inclusive, as it is possible for a creature to have a feat without meeting that feat's prerequisites. For example, a ranger can select Precise Shot as a ranger bonus feat without having the Point Blank Shot feat; he does not meet the prerequisites for Far Shot (which has Point Blank Shot as a prerequisite) because he doesn't actually have the Point Blank Shot feat, even though he has a feat that lists Point Blank Shot as a prerequisite.
—Pathfinder Design Team, 10/15/13
Sorry for the wall of text. The way I read these rules is that any spell-like ability of the appropriate level counts for the prestige class's prerequisite, and default SLA's are arcane, then the pixie's SLA's count toward the prerequisite. I couldn't find anything that would say how a creature would advance through the casting levels given by a prestige class without having any casting levels to begin with. In theory, you could just choose a base class's spell progression and go from there. This means low-level entry for several prestige classes, such as an Aasimar fighter, ranger, paladin, magus, or barbarian being able to take their 2nd level in Eldritch knight, for example. I also couldn't find anything that defined SLA's as spontaneous or prepared for prerequisites for classes like the dragon disciple. Although, I lean toward them being counted as spontaneous, because you don't prepare them, you just do them a certain number of times per day and then run out. I hope this was helpful.