If you are currently trying to sync your iPhone or other iDevice and you are receiving this message from iTunes: "Apps installed on the iPhone could not be determined," then follow these steps below to sort this mess out.
Step 1) Restart your iPhone by holding down the home button and the sleep/wake button simultaneously until the Apple logo appears.
Step 2) Restart iTunes. This fix usually solves the problem, but keep reading if it did not help you specifically.
Step 3) Restart your computer. Sometimes configuration files get messed up.
Step 4) Update all of your apps in iTunes and try to sync your iPhone again. This fixes most problems related to wrong versions of apps not being able to be installed.
Step 5) On iTunes, go to Preferences > Store and uncheck all the "Automatic Downloads" boxes for apps, downloads, and music.
Step 6) Using a 3rd party USB cable sometimes causes errors and unfinished, faulty syncs. Use the Apple USB cable for an error-free experience.
Step 7) For Windows only, go to Control Panel > Hardware and Sound > Device Manager. Click on your PC's name and on the upper level, click on "Action" and then "scan for hardware changes." Restart iTunes.
Hopefully one of these solutions worked for you. If not, explain the exact problem in the comments below and we will try to help!