To disassemble a Ruger P85, first ensure the firearm is unloaded by removing the magazine and checking the chamber. Next, pull the slide back slightly, and then push down on the takedown lever located on the left side of the frame. Once the lever is down, release the slide forward and gently lift it off the frame. You can then remove the recoil spring and barrel for further disassembly or cleaning.
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
100-400 USD depending on condition, accessories, box, manual, etc..
250 USD
You can get a manual for free at Ruger's website.
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.
Ask you local police to run the serial number. It has been reported it will show up.
100-300 USD depending on what "used" translates to in condition, accessories, box, manual, etc..