which versions of ios and os recognize each other

iTunes usually has a plug-in that it needs to download, and a restart into Safe Mode might get that connected.

If your Mac can get to Mojave (and it can), then that's where you want to be with existing and unresolved 32-bit app dependencies. Mojave is the last version with 32-bit support for older apps, so there are a number of other folks pausing on that version, too.

Apple prefers users to run the latest, and maintaining older versions tend to be more effort. The savings from not upgrading Adobe Creative Suite to Adobe Creative Cloud do come with increasing costs and limits, and the effort involved increases over time and not at a consistent rate.

Here, I'd install Mojave on an external storage device, try booting it, and get that working with Adobe CS6.

Then for better flexibility, install and then reconfigure that Mojave install as a guest within a virtual machine (Fusion, Parallels, VirtualBox, UTM, QEMU, etc).

If that all works, then look at upgrading your Mac main installation to current macOS, and running Adobe within the Mojave guest until and unless you decide to upgrade to current Adobe Creative Cloud subscription, or decide to migrate to an alternative app (Acorn, Pixelmator Pro, etc). Basically, boot Monterey, launch the VM, and run Adobe CS6 there, if you can. This does use more storage and does use more memory as compared with running it all natively. But it also means your main macOS install can move forward while you decide what to do with Adobe Creative Suite.

Follow on to earlier posting >>

There are reports appearing on the ASC Forums regarding failed installation of Monterey on older Qualifying Apple Computers. In most cases this is related to having a NON Apple Original internal drive ?  

The EFI Boot ROM included in Monterey is verifying for Original Apple Drive and if not found , may Balk or fail to upgrade to Monterey. 

Reports indicate the EFI BOOT ROM is Required to Flash the Computer and is a  requirement for a Successful Monterey Installation.

Plus tan new wrinkle to Installing Monterey to an External Drive specifically Monterey 12.3

Broken Monterey System Volume Seal

One maybe able to Install Big Sur to External Drive but will shelf the idea of Monterey for now

The external device test install being intended to test your configuration, without disrupting your primary install.

Which install is primary and which is secondary is your call, within the limits of the particular installed tooling.

I use Monterey as the daily driver and with 64-bit apps, with the Pixelmater Pro and Procreate apps used for editing.

External storage is useful for VMs, as those tend to be big. The VM files are probably not what you want to back up, either. Backing up what's within can require less storage for the backups than backing up the guest image. Better storage efficiency, if you're running TM or other tools within the guest.

Trying to install Monterey to an external drive will not be possible without first installing to the computer first. Monterey will not install to Non Apple Original Drives be it internal or external drives

If your computer doesn't recognize your iPhone, iPad, or iPod

If you see "Software update is required to connect to your iOS device" on your iPhone, iPad, or iPod touch

Makes sense to me, :)