Does RingCentral support Panasonic KX-TPA60 cordless phones? Also, does RingCentral support Polycom desktop phones? Thanks very much

They definitely support Polycom desktop phones but to the best of my knowledge they do not support any Panasonic models. Here is a listing of the phones they currently support (from their web site)
https://www.ringcentral.com/office/voip-phone.html