Hello,
I have 2 questions about ddrescue:
if I want to clone HDD with ddrescue in reverse mode (from 80000Mb to 0Mb), how must command line look?
when I brake clonning (example, ddrescue clones 4000Mb) and want resume clonning (from 4000Mb), how must command line look?

-r -s 8000M -m 4000M

should start at 8000 meg and copy a maximum amount of 4000 megs in reverse direction. The options may differ between build, therefore you should check with your version, it will tell you everything you need to know!

-m option You can find just in dd_rescue, not in ddrescue btw, option -r in ddrescue means exit after given retries (-1=infinity) [0], not reverse direction copy.
so, how to copy in reverse mode with ddrescue?