Anyone let me know where’s the documentation for this?
To be honest the search boxes anywhere on this site are useless.
There’s a passage in the Migration guide that you can find here under “Docs”:
https://developer.coronalabs.com/downloads/graphics-daily-builds
Scroll down to the bottom of the page to find info about V1 Compatibility mode.
Appreciate it Ingemar 
Sometimes just don’t have time to go through everything.
btw, narrowing your Google search to “docs.coronalabs.com” is also a good way to find what you’re looking for.
For example, the first result of this query will answer your above question:
site:docs.coronalabs.com compatibility
There’s a passage in the Migration guide that you can find here under “Docs”:
https://developer.coronalabs.com/downloads/graphics-daily-builds
Scroll down to the bottom of the page to find info about V1 Compatibility mode.
Appreciate it Ingemar Sometimes just don’t have time to go through everything.
btw, narrowing your Google search to “docs.coronalabs.com” is also a good way to find what you’re looking for.
For example, the first result of this query will answer your above question:
site:docs.coronalabs.com compatibility