You can link your existing account that you normally use. Progress on the BETA server is completely separate from the LIVE server. It’s based on a database snapshot when v.145 was released, so your progress will be rolled back slightly (when compared to your live account). And, when the new version is officially released, any progress you made on the BETA server will be lost. Also, any translation changes will also be lost.
Multiplayer games will work, however note that your network connectivity will not be correctly detected by the BETA server (I think it will always say “Port-restricted cone NAT”). If there is a discrepancy between detection and your actual NAT type, then you will not be able to join some multiplayer games (even if they are listed). If the discrepancy lies on the host side, then none of the guests will be able to connect.
Currently, the overdressed chicken’s red tinting – which shows how hot it is – seems to depend on its remaining health. This is more evident if you fight it in CI3U. Is it possible to make it depend on how many clothes it’s wearing?