Get App Version for my another app

There isn’t a way to get versions of other installed apps directly. However, apps from the same team can share information (for example, via an app group or a keychain access group) and you could have each app write their version on launch. This doesn’t meet your requirements exactly — the user could have the new app installed but have never launched it — but it’s close.

Also, are these apps targeted at general users via the App Store? Or deployed to a managed environment? The latter has more options available.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@apple.com"

Yes, @eskimo , Both apps are targeted at general users via App Store.

If we assume best case scenario, user has other App opened (and at that time if we fetch version info.) then we can store it via shared App Group / Keychain Access right?

Will it have any trouble when we Submit app on App Store (rejection issues) if I share version info. from one app to another?

If we assume best case scenario, user has other App opened

It’s not “has opened” but rather “has ever opened this version”. The basic idea would be for each app to make sure it’s current version in the shared store is up-to-date.

Will it have any trouble when we Submit app on App Store (rejection
issues) if I share version info. from one app to another?

That’s an App Review policy question and the only folks who can give you definitive answers about those is App Review.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@apple.com"