It is not, i didn't think it was necessary after cluster browsing was implemented, might look Into adding and option to see your own cluster next update
basically this means you don't have the Deluxe Battle Kit installed, it was supposed to auto rescue the error but i guess that's not working properly, you can either install the Deluxe Battle Kit, or go into the VMS_Battle_Handler file and delete the line of code "setBattleRule("noBag")"...
Plugin is not tested on the ebdx, it currently only supports DBK, i will be testing further those desync issues you listed, also, the plugin doesnt't have a version 2.09, did you mean version 2.09 of the ebdx? If so then they probably changed something in how battles are handled on that plugin...
This is very weird, i wasnt able to trigger any desyncs when switching pokémon here on my computer, can you upload a video recreating the exact steps to trigger this issue?
Also, about the not being able to battle on your own computer, i'll be honest and say i didn't really understand your...