If you are referring to the 33 round double stack magazine - I know it will fit the Ruger P-89. If the P-89 mag fits the P-85 your answer is YES.
You will need to contact Ruger for a correct answer
Ruger has sn data on their web site.
100-300 USD or so
Go to Ruger's web site and request a manual.
The original P85 had a design flaw which had the potential to result in an accidental discharge. The Mk II corrected this design flaw.
25-350 USD or so
250 USD
100-400 USD depending on condition, accessories, box, manual, etc..
Ask you local police to run the serial number. It has been reported it will show up.
Of course it depends on condition, whether its a MK-I or Mk-II, etc. but the value shows around $300 average.
100-300 USD depending on what "used" translates to in condition, accessories, box, manual, etc..
"Best" is subjective. A really good definitition of best is, the ammo that functions the most reliably in your particular gun.