Question:

After upgrading my device to the latest version of Android S OS (One UI 4), why were some of my installed applications deleted?

Answer:

When updating to Android S OS, apps that do not meet the new APK installation policies may be removed during the update process. This is a standard procedure due to the updated policy changes in Android S OS. To resolve this issue, simply reinstall the latest versions of the affected apps that support Android S OS and continue using them as usual.