Caution:- Backup ALL of your phone's data somewhere and try this method at your own risk.
1) Go to http://en.miui.com/unlock to get unlock permissions for your MIU Account. Use a Mobile Number based account and not an E-Mail ID Based account. Then you will be greeted with a form. Fill in your details and write why do you want to unlock the bootloader on your phone. Try to be as genuine as possible as they otherwise might just reject your application. Once you submit the application, It may take a few hours or days and they will notify you via an SMS saying that your account is ready for unlocking
2) Go to the same unlock link en.miui.com/unlock and this time they will provide a link to download the MiFlash tool. Download the zip file, Unzip it. Install MI Drivers first by right clicking on the file and running it as an administrator.
3)Now on your Redmi Note 5 Pro, Enable developer options. You can do that by tapping going to Settings>About Phone> Tap the MIUI Version 7-8 times. Then You can access Developer options by going to Settings>Additional Settings>Developer Options. Now Sign in with your MIUI Account(The same one used earlier) and also Put the SIM Card In of the same number that you made the MIUI ID with. Now you need to use a VPN to switch to China Servers. You can do that by Using PlexVPN or I have found this VPN App on some forums, which I have uploaded with this post. If you are using the latter app, select china Line 2 in server and press connect.
4) Once it is connected, Go To Settings>Additional Settings>Developer Options, Check the OEM Unlock Option On, Then go to Device Unlock Status, Here select the option of Add Account and Device. This will bind the device with your account. Now Backup all of your data somewhere and turn the phone off.
5)On your PC, Right click on MiFlash Tool, Run it as an administrator. Fill up your account details, The tool will check if you have permissions or not. If all goes well it will give you instructions to connect your phone in fastboot mode. So press the volume down + Power button on your phone until you see the fastboot screen. Now the Tool will ask you for your permissions, Grant them and Voila! Within 5 minutes it should unlock the bootloader on your Redmi Note 5 Pro. If you'r eunlucky, you might get a message saying try after 360 or 72 hours. So you will have to wait. I personally got that error with my email ID based account, But it worked well with my mobile number based account
So that's how you unlock the bootloader on your Note 5 Pro. I have also rooted my phone and tried to enable Camera2API but the front camera crashes on Enabling Camera2API. But if you guys still want a tutorial about rooting this phone, let me know. I will make that too. Here is a video of the whole process, You can watch it.
Thanks for Reading!