Use bitbake command line to override or modify variable


1. Where to learn more about above command options (file path the file referred to to be found; file path usage in command option,....)?
2. Set/modify variable in bitbake command line, e.g. BBPATH="xyz" bitbake <target> - does this support all supported kinds of variable expansion?
3. Any build process variable classes exist of which the settlement or modification in way as (3) does not work?
4. Any build process variable classes/types exist for which to set or modify it in way as (1) does not work?

5. Any use-cases exist for which -R, --postread, -r, --read to be preferred choice compared with (3)?
6. Any use-cases exist for (3) be better choice compared with -R, --postread, -r, --read?