@PummyRaj gave two ways to find for the game version on an iOS device.
1 Go to "Settings" ---> General ---> Storage ---> List of all the Apps displaying which App takes how much space will be showed ---> Tap on Farm Heroes App ---> You will see the version.
In iOS v7.1.2 the way is --> Settings --> General --> Usage --> Farm Heroes...
2 Open the "App Store" ---> all of the games that we have installed will be listed there ---> Select "Farm Heroes Saga" ---> Do not click on Open, but just tap on the name of the game ---> Details of the App will be displayed