Hello again!

This is my second question about HDDs.
When reading the recovery forums I often see "you should write the valid P-List hex module there, but you don't have one" or that [i]"after changing PCB it won't work, because some unit-specific values are missing or incorrect".
Moreover I have heard about bad HDD series that can overwrite Service Area or that are failing after a power failure.

My questions are:
1. Is there any possiblity to make the backup of as many as possible modules in Service Area when using programs like HDDL and only standard PATA, SATA controllers + some PATA<->SATA converters? How many informations can I retrieve by such method & which modules are important to save for the future data recovery?
2. Is there any method to retrieve informations from HDD's PCB components? What is important?

I am sorry if those questions are stupid/bad, but I have not found any unambiguous answer so far.
I am sorry for my English in advance.

Please answer me.

With best wishes
adam