create virtual terminals with single ssh connection

How to create virtual terminal from a single ssh connection?
How to have multiple terminal screen from a single ssh connection?
How to disconnect / reconnect back with running download jobs after disconnecting from ssh?
How to re-establish pending jobs and restore screen after exiting ssh connection?
How to detach and reattach ssh connections?
How to know which tty does your current ssh connection is connected to?
How to restrict root logins via ttys and vcs?

Here's a quick and brief way on how to do this stuff.