What does the permitting process look like and getting the zoning changed? 

Permitting.

Oakland permit department is telling me Category 1 ADUs require separate addresses, and therefore, separate metering.

Assuming you "converted" the property to rental 4-5 years ago and you filed for rental applications/permits and have been filing 1040's for that property then you should be good from an age perspective. 

All the same permits and inspections should be required whether the home owner does the work or not.

The city doesn't count it though because of how it was permitted. 

The non-buildable tract of 15 acres was being sold to a farmer for crops, not houses and they were not permitted because no building rights were remaining. 

Homes with active permits can transfer to the new owner but unlicensed properties will need to wait for a license until the currently active rentals drops by roughly 100 licenses.

They forged documents, have the assessor for king county as one of their CEOs (my property was in Clark county WA but my property title was changed in King county WA where he WAS the assessor) hsbc had to pay me and countless others for bad foreclosure practices and that caused them to go bankrupt and my loan was floating and I essentially owned home free and clear due to terms of the contract stating that if loan was to be sold that hsbc my husband and I and the new proposed lender had to all meet in person and sign new paperwork permitting the transfer of the loan which never happened.

Especially considering zoning approvals, permits for land development (Local and State) moving equipment in, then permits for individual houses before you can even sell or market.