In the search box enter the device name or code name.
From the results choose your desired model.
Then select the codename of your smartphone.
Afterwards, you should see the list of CSC, Country and Carrier. Let’s use this database to choose appropriate software.
Next, you should see the table with information about your firmware. If everything is correct click on DOWNLOAD button.
Unpack and open the folder. Then let’s launch the Samsung HARD Downloader.
The app should show you the information about your firmware. In order to save the software select the DOWNLOAD button and choose the desired location.
Wait until download end, next unpack firmware by 7zip or any other packer.
Great work, you are ready for to next part.
Changing firmware in the phone will erase all of your data !!
All described operations you are doing at your own risk !!
If want saves your data do a backup before starting!! !!
If want update your phone to Android Oreo firmware must use the Odin3 v3.13.1 version or higher.
Samsung Firmware Change/Update by Odin
Before start check, if the phone has a battery charged at least 30%.
Connect your device to the computer via USB cable.
After that, you should check that you have installed Samsung drivers. If not install from here Samsung Drivers
If you have installed you will see ID:COM field highlighted and also in log Added.
Make sure you have selected Auto Reboot and Factory Reset Time options.
Select the Correct image like on the picture if you want to change firmware with data erase. Note! If you got only one file upload it as AP file.
If you do not want data to erase but just to update the android version to higher (region must be same as in phone if not phone will only reboot on the logo and never turn on), just use a HOME file like CSC file (when is an archive that you downloaded or just download firmware from samfirm with unchecked option BINARY NATURE in this situation you will have firmware that has only 1 file)
Check everything again, and press START.
Your device is updating now, be patient it can take a while.
Your device has been updated. Now, you can disconnect the device from the computer.
Warning! After the start, you should not disconnect the device from your computer.
How to Change / Update Firmware in SAMSUNG Galaxy S21, How To - HardReset.info