If I am playing a human with the Divine Blessing (Hylax) feat, the Extended Telepathy feat, and the Phrenic Adept archetype, do I have limited telepathy out to 120 feet? Why or why not?
You have limited (with caveats) telepathy out to 120 feet, because Divine Blessing (Hylax) gives you the equivalent of limited telepathy racial trait (30'), Extended Telepathy extends it by 30', and Phrenic Adept (2nd level) extends it by 60'.
Bonuses that do not list a bonus type do stack, both with each other and with all typed bonuses. Such bonuses, often referred to as “untyped” bonuses, are among the most utilitarian of all bonuses in the game.
These seem to be bonuses without a type, so they stack on your base 30' range.
Additionally, Divine Blessing (Hylax) combos with Phrenic Adept (2nd level) to allow you to communicate with those who are friendly or helpful even if they don't share a language. Plus, Phrenic Adept (2nd level) combos with Extended Telepathy to allow you to attempt a Mysticism check to communicate with a creature who doesn't share a language with you but does speak some sort of language.
You don't have full telepathy.
I had concerns, since Phrenic Adept says the following:
Since I got limited telepathy from a feat, and not from my race, I was thinking it wouldn't stack in this case.
However, you're right in that the Divine Blessing feat says "" which implies that it is treated in all respects as a racial trait--and support the increased range stacking.
Thank you for the clarification.