1) Yes.
2) Yes, pin-out details for 8 wire cabling can be found here:
http://knowledge.digi.com/articles/Knowledge_Base_Article/Cabling-Pin-Outs-for-Digi-PortServer-TS-MEI-RS-485
3) I'm not aware of Digi providing this cable. You might want to reach out to Digi Sales to confirm this.