Question has been asked and answered may times. There is not a factory restore "image" on the CMU that can be used to restore it to factory fresh like some PCs come with. There is also not a BIOS mode that you can get into from the screen that might let you load an OS like a PC.
CMU firmware updates are "incremental" and do not include all CMU OS files - only the changed ones typically. This means if if you edit/change file "a" on the CMU and it is not on any firmware versions (past or current) then a firmware update will not fix the problem. In those cases you have to have a copy of the original file which is what AIO does. HOWEVER - if your change results in a reboot issue then you are limited in how to gain access to the CMU to fix the problem.
Worst case is you have to have the CMU replaced, next worst case is someone (
search the forum) has figured out how to gain access to the CMU through a hardware programming port but it requires hardware and software knowledge and experience. There are other less crippling boot loops that can be resolved through persistence - see the
Infotainment Index for details.
