Update...

After getting their response " I can assure you that we do not sell things that do not exist."

I replied "...your explanation states that a schedule change necessitated my downgrade from first class to economy. While this might be the case, no details have been provided to substantiate this claim. I request explicit information about what the original schedule was and what changes were made that supposedly required the downgrade. Without these details, your statement remains unsubstantiated and does little to assuage my concerns..."

Alaska: "... We want to assure you we have reviewed your concerns again to ensure you have been treated fairly. Unfortunately, we are not able to provide you with the evidence you requested. We're sorry you feel our compensation is inadequate. Unfortunately, for your situation, we cannot offer additional compensation..."

I replied "...I am perplexed as to why Alaska Airlines is unable to provide me with the evidence I have requested. I am not asking for confidential or sensitive company information, but rather for evidence pertinent to my own travel and booking experience, which I believe I have a right to know. Specifically, I asked for documentation or proof that links the schedule change to my downgrade from first-class to economy. Additionally, I requested information about the "P" class ticket, which was sold to me as a first-class ticket but was later revealed to be an economy seat by Hainan Airlines. The lack of response on this particular point raises serious concerns for me about the integrity of Alaska Airlines' sales practices.

I would appreciate it if you could explain:
Why you cannot provide the evidence requested: Given that this pertains to a service I paid for, I'd like to know the reasoning behind the lack of transparency..."

They knew they sold nonexistent tickets, told lies, and could not provide evidence to underwrite what they did and said.