I have Windows 10 1809 Enterprise. When I restart Windows, the applications that were open are closed after restarting. Weren't they supposed to reopen automatically after 1709?
Enabling the re-opening of applications is done in Settings > Accounts > Sign-in options. Place a check-mark next to "Use my sign-in info to automatically finish setting up my device and reopen my apps after an update or restart".
For more information see the article Turn On or Off Use sign-in info to auto finish setting up device and restart apps after update or restart in Windows 10.
However, not all applications are relaunched after a reboot, and the reason is that to be eligible for restore the application must register itself for restart through Windows API. As this is a new option, not many applications do this, which is true even for many Microsoft applications. You will need to find which applications support restart by trial and error, but this might improve in future versions of the applications.
For reopening folders, this is a separate option in Windows Explorer, accessible via the View tab on the ribbon, by clicking the Options button. You need to enable here the option of "Restore previous folder windows at logon".