The only legitimate way to put the older version of an app on your iPhone it to download it from iTunes on your computer if you still have it stored there.
In addition, if you are running an earlier version of iOS on your iPhone, Apple now allows you to download the latest compatible version of an app from the AppStore, if the developer allows it.
Discussion of any other methods of obtaining an older version of an app are not allowed on these forums. With that, this thread is now closed.