Question

I would like to know whether the Cache directory gets deleted when upgrading iOS?

Answer 1

There are no clear answer for this in the documentation. It can be purged when the device gets low on disk space or performing a full restoration.

Application_Home/Library/Caches

Use this directory to write any application-specific support files
that you want to persist between launches of the application or during
application updates. Your application is generally responsible for
adding and removing these files. It should also be able to re-create
these files as needed because iTunes removes them during a full
restoration of the device.