Pre-Sales Questions – private messages, roles, notifications

I have a site on which we match two users (two different roles) regarding a specific service (let’s call it a transaction).? I would like only the two users involved in the transaction to be able to chat on a page.? This page is accessible to all subscribed users, however, the data on the page is dynamic?depending on which user is logged in and at which transaction he’s looking.??e.g., User A is the seller and User B is the buyer for transaction X and User A is the seller and User C is the buyer on transaction Y, so on a page, in the first case only A and B can chat and the second case or A and C can chat.

Here are my questions (for any answers that are “yes” please cite the documentation page on which the solution resides):

1. Is it possible for me to dynamically assign only two users to a chat and make sure that each time the page is shown it only shows the chat between the two of them?
2. In the documentation, it says that the access is only for the following roles: subscribe, contributor, editor, author, and administrator.? Is there no option for custom roles? All my users are assigned a custom role when they subscribe.
3. Is there a hook into the action of a user sending a chat so I can send my own push notification or something similar?