Thank you for your question. Please permit me to assist you with your concerns.
To ensure that I do not miss anything, I will go line by line with my responses. You asked:
In California, San Diego. What responsibilities does an HOA board have in respect to maintaining the inside wall plumbing.
That depends on the bylaws and the CC&Rs. Typically those documents will define whether common areas that are between two units are maintained by the adjoining units or the Association. There is no one answer as it is based on the language in the documentation.
Who is responsible for flooding damage in a condominium when cause of damage is old pipes bursting inside wall.
Likewise, this is based on the bylaws and the CC&Rs. Sometimes the Association is liable, other times if the break was in a common area between two or more units, those units are responsible.
What responsbility does the homeowner have.
Again, the CC&Rs point it out.
The shut off valve for hot water in a specific unit cannot be reached as it is on the roof, The main shut off is locked up and no key access for homeowners in an emergency. The interim time of getting someone to shut off water and flooding happening has resulted in so much damage. My HOA will not let me file a claim with the Association's Insurance, they refuse. Does State Law Supersede HOA docs for this issue?
State laws supersede if the bylaws violate the law, but if the law is unclear (and here there is no one answer), the bylaws control as there is no state law that regulates specifically what the Association is responsible for and what it isn't.