I have reviewed the post comprehensively. You've done a remarkable job of troubleshooting and have shown great resilience to try and get the issue resolved. Kudos to you on that score. As @Riddle_Decipher is out of office today, I am taking over from here.
Please run component tests on all computer components predominantly the fan from this link:http://support.hp.com/in-en/document/c03467259 please perform all the steps from this option " Running the UEFI Component Tests" If any component fails please make a note of the failure code and then contact HP phone support to get the computer serviced.