The answer to the question as asked by the OP is what TA said...It is equipment dependant.
FWIW if you are trying to fly an LNAV/VNAV approach to a runway where there is a coincident ILS then (certainly on some types) selecting Approach Mode (APR] will probably lead to the AFDS on your equipment coupling to the ILS and ignoring the LNAV/VNAV profile completely....Certainly on those types if you want to fly an LNAV/VNAV approach you definitely do not select APR.