Forbidden Knowledge states that "adhere to the rules of taking traits as if you were of that Domain"does this mean when taken we must adhere to the additional rules for the branch as well. Reptilica bloodlines were covered in the description, but the certain Fey traits (Primal, Celestial, Infernal) have additional rules to them such as not being able to take Tier 2 traits if the correct path has not been taken as well as being unable to take from both Light and Dark traits together.
If taken through the use of Forbidden Lore are we bound to the sphere of Influence, Evolutionary Branch, or Classification, or Lineage restrictions as well?
Your faction would still be following the caveat that you would not be able to take Infernal 2nd Tier Traits since you selected the Path of Twilight.
Celestial, Infernal, and Primal all have those restrictions and the traits in that 2nd Tier are a little more powerful or focused. If there was one trait specifically that you were looking for in the 2nd Tier taking forbidden lore could get it for the class with forbidden lore (like Nether Lord). However since your faction was not created in the Path of Darkness, the rest of your faction would not be able to take 2nd Tier traits.