A
What device are you asking about?Just downloaded it already don't like the task bar or the changes made to the slide down menu.
Welcome to Android Central! You can find the version number in Settings>About Phone. But most likely, you updated the phone to Pie (9.0). The only way you can roll back the update is to flash the previous Oreo firmware using Odin (http://forums.androidcentral.com/am...w-flash-stock-rom-via-odin-new-interface.html).
You might be right on thatIf they have a security patch later than March, if you have a USA device, they relocked the bootloader. Flashing to firmware earlier than that may not work anymore.