In order to update your app to the latest version, go to the App store > "Updates" tab > Hold your finger on the screen, pull down and release your finger. This will refresh the page and you will be able to update.
It's really strange that it doesn't download data to your app on your iPad. So I try to transfer my data from my iPhone to my iPod touch and it works like this:
1) Open the newly downloaded app
2) Hit "Tap to start!"
3) Hit "Link Nintendo Account" > This should take you to Nintendo website
4) Sign in using whatever Nintendo account you use for your AC
C App on your phone
5) After you sign in successfully > Hit "Use this account" > It will take you back to the App
6) You will see a message that says: "Your save data is now available to be downloaded from your linked Nintendo Account" > Hit "Return to Title"
7) Now you will see: "Data download ... save data is approximately ..." > Hit "Begin"
8) After you're done downloading, you should see a screen that says "Data update finished. Returning to game". Then it will take you immediately to where you last left off on your phone. No tutorial screen at all.