The basic answer is YES.The state of MI does not set up any requirements for volunteer law enforcement(reserve/auxliiary) in the state. Standards are left up to the local jurisdictions.There,...
When? It isn't illegal or anything yes they can. Added: Absolutely - and they can demand that you produce identification if they have reason to believe that you may be impersonating one.
If you are a police officer you would not need to ask. A police officer doing his duty will treat another police officer as any member of the public (if they are out of uniform and off duty).