New answers tagged multi-user
Solved in Android 5.0 (built-in feature).
Yes. In Android Lollipop it is possible to have multiple separate user accounts with separate apps and app data. So your apps and its data won't be mixed up. If you don't want to switch or couldn't update to Lollipop then you can use apps such as tasker or Nandroid backups as Stephen suggested. Read more on Multiple User Accounts in Lollipop.
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