1) Is dev/test/prod on same LPAR? Yes
2) Is dev/test/prod on same box? Yes
3) How frequently are promotions from dev to test allowed? D.
a. No restrictions
4) Does separating DEV from TEST require more time & effort for a given development project?
This appears to be asking about the time to break dev/test/prod out between boxes or lpars, and we don't do that, so I have no answer.
5) What would be some reasons why this is a good idea (besides the auditors told us to)?
Guaranteed to not screw up the production environment.
For our testing, we use the library list to control our impact. A lot of our testing uses STRDBG as an added measure to not impact any production libraries.