ConverseKit allow to start chat for ALL users?

Hello. I use EasySocial on site.

A. And users asking about any "chat" that allow to communicate ALL registered users in one place.
I suppose it's not possible? It works the same way as Conversation in EasySocial? Somebody can create conversation "For everybody" but new users still need to be invited to join it? User can't join conversation by himself? Or user can't be auto join to conversation after registering?

B. Also question about price:
1) seems I need to pay for ConverseKit every 6 month (to get support and latest version)
2) but how often I need to pay for ConverseKit Desktop (can't find info)? Once?

C. I downloaded MacOS version of ConverseKit Desktop but it ask to type login / password. demo/demo is not correct. How to test it with http://conversekit.stackideas.com (screen attached)?

D. Does ConverseKit and ConverseKit Desktop already have Russian language or I can create it by myself?

Thanks.