It is possible to get the full list of updates that has ever been released for your device but you simply cannot downgrade your device without formatting your phone.
If you still want to proceed with the downgrade, I strictly recommend you to backup all of your data, contacts, important personal informations, pictures etc. to a safe place like your PC
Once you proceed, there is no turning back and all of your data would be lost forever.
You can get the full list of updates that has ever been released for your device by typing in your exact Samsung Galaxy J7 Prime model in the search box of https://samfrew.com/all/.
This step is very important, make sure you select the correct model for your device. Selecting the wrong model would result in bricking your device and rendering it unusable without getting help from professional services.
You can find your exact model on the phone's original box or by using "Settings". First on your phone, go to "Settings" --> "About Phone" --> "Model Number"
Note: If your phone model has a "/DS" behind it, you can safely ignore it.
You would search your model without the "/DS" like this "SM-G610F" in the search box.
In this case, my J7 Prime's exact model is "SM-G610F/DS". So, I would type in "SM-G610F" as the model in the search box and proceed with selecting the country and the choice of firmware that you would like to download that is around February 2019.
Once you've download the firmware file, you should have a file like this "xxxxx.zip" where xxxxx is your firmware file name.
For example I want to download J7 Prime firmware for my country Malaysia (XME) and I want the latest firmware. So my firmware file name is "XME-G610FDXU1CRL2-20190108182010.zip"
After completing all those steps, continue with the following:
Use your original Samsung USB cable that came along with your original box like the image above
Unzip the Samsung USB Drivers file and install the driver. Follow all of the instructions in the driver installation wizard.
Unzip your firmware file (the xxxxx.zip file) and you will get a file with xxxxx.tar.gz, xxxxx.tar.md5 or xxxxx.tgz
Unzip Odin 3.13.1 zip and open up the application. Once inside, tick the box beside "AP" like the image above.
Press "AP" and select where your firmware file is located (the xxxxx.tar.gz, xxxxx.tar.md5 or xxxxx.tgz file)
Boot your phone into download mode. Press and hold "Power" button + "Volume Down" button + "Home" button together until you see a green background with text like the image above then read the warning carefully and make sure you want to proceed. Press the "Volume Up" button to accept
Step 8: Plug in the Samsung USB cable to your PC and connect it to your phone
Step 9: Press Start in the Odin app on your PC to start flashing the firmware
After flashing, Odin app will show a big green sign with "PASS!" and this indicates that your firmware flashing is successful like the image above
Reboot your phone, wait for Android to start loading everything. Complete the first setup and go to "Settings" --> "About Phone" and you should see that your firmware has been downgraded to February 2019 firmware