Please, read the tutorial → APIM Sync Settings Not Saving, VER_ERR08 Errors, Cannot Perform Master Reset or Upgrades/Updates (Solved)
It’s really well explained, I won’t be able to explain it better than it’s there… If you have specific questions or doubts, just ask… But “how” is broad and generic, plus “how” is explained in the uide.
Since the RWdata cleaner tool does not work for you, you will need to attempt the other methods described in the “Historical Solutions” section of the guide.
You are stuck until that happens, since Sync3 won’t be able to process any upgrade USB.
So once you make enough room with those procedures you will be able to either reformat the unit (clean start, which is recommended) or just installing Sync3 3.4.23188 without any other package (this build has de solution for the rwdata partition issue as well).