ios 14 compatible with itunes 12.8.2.3 (high sierra 10.13.

Does High Sierra sync iOS 14?

macrumors 65816

YES they will – because Reminders and Calendar on both iOS & High Sierra sync via iCloud; your versions are not an issue.

What iOS is compatible with High Sierra?

Requires MacBook Pro with Touch Bar, iPhone 6 or later with iOS 10 or later, or an Apple Watch with watchOS 3 or later.
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Supported by the following Mac models:

• MacBook (Early 2015 or newer)
• MacBook Pro (2012 or newer)
• MacBook Air (2012 or newer)
• Mac mini (2012 or newer)
• iMac (2012 or newer)
• Mac Pro (Late 2013)