What you’ve asked is a lot for a forum such as this – so I’ll shorten it considerably.
1) Register at cisco.com as either a customer (if you have a support contract), or as a guest if you don’t. Even guest status gives you more access than the general public.
2) Set up a TFTP server, and perform a copy of the IOS and configurations on a regular basis.
There should be some tutorials on cisco’s web site.