Free scanning tools to check OS & network security hardening / compliance

Q1:
I know Nessus used to be free but not anymore but I don't mind getting
an old free copy of Nessus just for some refreshing to familiarize.  let
me know if where I can download

Q2:
Also looking for non-intrusive tools (ie those that don't make changes
to the OS / apps / DB) that collects info like password strength, password
locking is enabled, non-recommended services like ftp & telnet servers
are disabled, when was the last security patch updates for Windows
2003/2008/2012 & MS SQL, Linux, Solaris

Q3:
For network switches/routers, looking for tools that ensure hardenings
are done, eg: on Cisco switches, we want to verify if "no ip http-server",
"icmp unreachables" etc are implemented.  Let me know any free tools
I can get to do these