I've received an old iPad to play around with running iOS 9. Safari is essentially crippled by a lack of software updates but old versions of the apps can still be installed.

Because of Apple's great software design, you need an old version of iTunes. From there, you can add apps to your account. Then, on the iPad, you can install "purchased" apps. The store itself is completely useless as nothing will install, but the "purchased" page will let you download the last version that works on the device.