Each tab can have completely different content, so in effect each tab can be a report. If they need to be physically distinct documents then the closest to what you need to achieve is probably going to be achieved using the opendoc statement. Don’t know what that is? A search on opendoc will return many useful results!
This is not possible. Each of these reports (A & B) is considered to be an individual document. The tabs in documents are referred to as reports. Documents can have multiple reports but you cannot attach one document to another to get multiple report tabs.