I am trying to extract an app that is no longer in the app store form my old phone (iPhone 6 - IOS9.3.5). Is there a JailBreak for 9.3.5 that wouldn't require the phone to be wiped before installing as that would defeat my purpose?
Have you checked your app store purchase history to see if the app is there?
As far as I can determine, the only iOS 9.3.5 jailbreak was for 32 bit devices. Your iPhone 6 is a 64 bit device as are all iPhones from the iPhone 5s and newer.
I see the app in purchase history, but don't see any link to download it. it also doesn't come up in a search of the store apps. Any way to retrieve this app (I have not previously download it to computer)
If you check the purchase history on an iPhone that does not have the app installed, you should see a cloud icon with a downward pointing arrow. Tapping that will download the app to your device.
If you intend to install this app on an iPhone on any version of iOS 11, it may not download if the app hasn’t been updated in the last couple of years to be 64bit compatible. If you check your purchase history on a 64 bit device that doesn’t have the app installed, the cloud icon will be greyed out and non responsive.
If you have ever synced iTunes and have it download apps you may have it on your computer. With earlier versions of iTunes and iOS I have, in the past, been able to drag an app to my iPhone, hooked up to iTunes, to install it from my computer