Is there any step by step information document that states the approach one should have for maintaining backup of Spectrum and its components in case a recovery is needed.
I'm aware of maintaining backup of SS and DDM databasesAlso there is a need for maintaining backup of custom folder.Is there anything else that is needed?
You could start with the instructions for building a Fault-Tolerant environment.
If you have a working SpectroSERVER set-up with a OneClick able to access it, that should be OK. You indeed need a DDM and an SSDB backup of the same version of Spectrum, and in case you have to start after a disaster, you just have to restore the backups and you're good to go. The "custom" directory can be copied/pasted over. You can of course schedule a regular backup/restore for the server to be ready anytime (or once a week or so).
Another very good option to explore for Spectrum is "simply" to have another FT server which is remotely located on your DR site, so it's always up and running, ready to take over in case of failure.