Clarification on my options for backup and restoring my phone

[M_J_B]

I have been browsing the forums for a little bit and am still a bit hazy on my options. I recently purchased a used iPhone 4S. It is on iOS 7.1.2 and I would like to try jailbreaking. My concern is that I have a solid backup in case I would like to come back to vanilla iOS. I would also not like to be forced to update to iOS 8 if I choose not to.

What is the proceedure to make a backup that will allow me to restore my device to the current iOS 7.1.2 that is currently installed? I have no interest in preserving apps or data since there is nothing that I can live without or just redownload.

Can I keep a "copy" of the backup, upgrade to iOS 8, later decide to revert, and restore this "copy"?

I have read the few pinned topics on this forum and I'm not sure if the coffee is not kicking in but I'm not seeing a clear yes or no and if yes a clear set of instructions on how to do this.

Thanks for any guidance on this. I really apologize if this is clearly spelled out somewhere else. Please point me to that page

 

[scifan57]

The signing window for iOS 7.1.2 could close at any time now. Once that happens, the only iOS version you can restore to is the latest version; in this case, iOS 8. There is no way force a restore to an iOS version that is no longer signed by Apple.

 

[willerz2]

As stated by Scifan57, once the signing window closes, there's no way to restore back to an iOS that is no longer signing (publicly speaking). This is the case regardless of backups and measures taken. Backups do not include system files for the most part, much less the iOS as a whole, similar to that of Android if that puts it into perspective. Backups only retain user data, so even if you backed up on 7.1.2, went to iOS 8, after which iOS 7.1.2 stops signing, and you wanted to revert back to 7.1.2 from iOS 8, you cannot do so. The last device to publicly be able downgrade is the iPhone 4 which is not supported by iOS 8.