No, no... you need separate backup, just in case anything goes wrong... and they do from time to time...
However, the A&I will not delete any of your data or 3rd party applications, if all goes well. So with a bit of luck you will never need the backup.
But, as I said above, never perform any large installations without current backup, the risk is too big for a hiccup to occur... and without backup that may cause you to loose all your data.
Also, backup is nice to have, on a general basis. You never know when your HD will crash beyond repair, your computer will be stolen, there might be a fire, etc... you get the point. There's an axiom that goes something like: Everybody will loose all their data at least once in their life. And if you don't have backup those data are lost forever. 🙂