Since the Gateway 3DS official team has released the latest firmware GW_ULTRA_3.0.1 and downgrade file, many people would want to know how to downgrade 3DS firmware version 4.6-9.2 to 4.X now. So below is the tutorial step by step to be provided to our customer.
Notice: if you are very new to know how to downgrade, there is no need for you to do it since Gateway 3DS now can work on 3DS firmware version 9.2 or below and downgrade may brick your 3DS console.

Let's begin our tutorial:
1. Download Gateway 3DS Ultra 3.0.1 and Gateway.dg file(for EU here) specific to your region and MD5 Checker.

2. Decompress the MD5 Checker and then choose the gateway.dg file by clicking add and navigating to where the file is located.

3. The MD5 Checker display the name of the file would be seen where it's located and the MD5 after choosing the gateway.dg file and opening it. Go to where the MD5 is and right click then compare MD5. You can paste in the MD5 for the gateway.dg file you downloaded already. If the MD5's match we can move on to the next step but if not, please make sure you download the right file and re-downloading the file itself.

4. Back up your Nand now to your internal SD card of your 3DS console via the Gateway launcher. Press A to "Backup System Nand" and "Start" to start the backup process and it may need 5-15 minutes.

5. If you have finished backing up your Nand then exit the gateway launcher and turn your 3DS console off. Take the SD card out from you 3DS console. Insert your SD card into your PC and open it up so you can view the folders and files. Make a copy your NAND.bin and put it on a safe place on your PC. Your original NAND.bin on there will be needed to do the downgrade. Then put the Launcher.dat from the Gateway Ultra 3.0.1 files on your SD Card along with the gateway.dg file.

6. Now confirm that both Launcher.dat, gateway.dg and Nand.bin files are on your SD card. Then take out it from the PC and insert it into your 3DS console.

7. Now boot your 3DS console and open the web browser. Enter the URL or prepare to open your bookmark and go to the website. Turn your wireless communications on then go to the website and wait for the Gateway menu to boot. Then navigate to Downgrade Console at the end of the menu. Then press A on downgrade console and follow the instructions onscreen. It is suggested that plug in your 3DS to avoid any type of power problems as seen in the photo above.

8. Gateway program will take 5-10 minutes more or less to do below thing. Just wait for it. You should be taken to the shutdown screen as seen in the photo when you finish except it'll say software has closed. Then choose power off.

9. Turn your 3DS console on again. You should be back to one row like a normal 3DS fresh out of the box. Please confirm that Turn Your Wireless Communications OFF! Then go to the System Settings and check your firmware.

Now all the steps has been told. Then if you see your firmware version is 4.X, the downgrade is succeeded! But if not, I'm really regret that your 3DS console may be bricked already (a black screen perhaps pop out and not boot into the normal 3DS Menu) and no solution will be provided for now. So I repeat again that you must think twice before you downgrade!

Enjoy your newly downgraded 3DS now!