how to downgrade using time machine

This has nothing to do with Time Machine.. That is to recover files on the Mac.

You can recover files via iTunes that you used to backup your phone.. however you cannot downgrade firmware.. Just like a Mac .. it is extremely difficult to downgrade an OS from Time Machine.. unless you fully saved the previous configuration and did not let the new install touch it.

Restore iOS to earlier version AFAIK is a hack.. I am not allow to give hack info here.. so google for it.

For Apple iOS upgrades are always one way.. up.. never down. AFAIK..

(If I google downgrade iOS to 8.3 there are plenty of sites with info.. none official.. none on discussions or any website apple is connected to).

Or am I confused about back ups of an OS vs files?

Yes, this is the problem.

When you backup an iphone you are not backing up the OS of the phone.. you are backing up the files.

There is no mechanism provided by apple to restore a phone to older OS.. all iOS upgrades are one way.. up..

(After a fast google when 8.4 was released you had one week to restore to 8.3, after that the method of downgrading was removed.. ie Apple deliberately stopped users downgrading).

You can recover your files.. you can load the files into the new OS on the phone.. but you cannot restore a phone to old firmware.. at least not by any mechanism apple gives you.

As I stated I have an untouched 8.3 install file sitting on my desktop, that I downloaded the day before apple changed over to the 8.4 version that I now have on my iPhone.... are you saying that this file is useless?

If you attempt to downgrade it won't work.

What I am telling you to do is look outside apple instructions for how to take your phone back to earlier firmware. We are not allowed to post here what apple considers to be hacks. (within reason). Just google for it. There are ways and means to do most anything.. I do it on lots of stuff but I am simply a person who is too old to believe the latest upgrade is the greatest so I never do it.. I have my iphone and ipad on much older iOS so I have never needed to hack them.

Let me just say that I'm pretty new to the apple world, having just converted over from bill gates world about a year and a half ago

Remember apple sell hardware and MS sell software (primarily). Apple control that hardware.. MS do not care a hoot about your PC.. You can change hardware as you like.. Apple do not allow their hardware to be altered in any significant way. At least not now.. more and more computers are sealed up.. you cannot replace anything. You cannot even open them without special tools and breaking seals and warranty. So if Apple decides that iOS when upgraded cannot be downgraded.. they enforce it as far as possible.

You are not spending the time you need to on google.. there is plenty of info out there on how to do this.

As in my time machine only backs up files, not an OS for reinstall? The same as your explanation in regards to my iPhone?

The Mac OS is saved and can be reconstructed from the TM backup. It is not like the iphone..

However it can be easily corrupted if you load a new OS and try and backup to the same backup.. so great care needs to be exercised.

which I could use again if i needed to do a reinstall, looks like you're telling me that that is impossible with apple?

You can use your previously downloaded OS and reinstall it.

However if you want to download the previous OS and have not purchased it.. or since OSX is free upgrade.. at least downloaded it.. you will find apple block you from downloading.. I discovered you really must download every update. so your iCloud account has a record of your using each and every one.. but do not install it.. once downloaded just copy the file to another location for safe keeping. If you ever need it in the future you then have it available.