When user sending first message on your support whatsapp number, it will be assigned to any one available agent who is online.
If a agent is not online, the conversation will be kept by "whatsappbot" user. And as soon as a agent comes online, the chat will be transferred to that.
Sometimes Yes. In Gold Plan Only, we can fetch old chat history to some extent. In Silver Plan this facility is not available.
We can not guarantee what all can fetched, it all depend on the whatsapp web state.
This is not a good practice to do. In any support system, agent chats are separate separate. But a manager and admin can see all the chats.
If you want to do, follow it at Handling Chats
Yes, you can send/receive all type of Media. Please note that in Silver Plan, all the outgoing media will go as link.
Under Silver Plan only, you have to keep open whatsapp web at your end.
In Gold plan, we will keep the whatsapp web at our end after you scan a QR code while setting up number. So you don't have to worry about it.