MESSED UP my phone's DEVELOPER OPTIONS but would like to get it back with my data

[Sebbchen]

My issue is that I went into developer options and apparently went overboard on changing a value to scale UI (minimum width value). The phone crashed and is not able to fully launch the system anymore, then restarts and enters recovery mode. After some time it reboots automatically, so it's in a bootloop from what I've heard. Mi recovery 3.0 has the options "connect to Mi PC Suite", which I installed on my Laptop and connected, but only gives access to flashing. The other option is a data wipe, but I would really like to maintain my data.

Basically what I need is a way to change the value back or at least backup my data.

I am able to enter Fastboot, but don't know how to use it.
My phone is a Xiaomi Mi 9T Pro running MIUI 12 / Android 10 without any root or modification neither a unlocked bootloader.

 

[ThatLatinGuy]

Try entering in safe mode and see if it works normally , if it does try erasing the data of the settings app and try a normal boot

 

[Sebbchen]

Try entering in safe mode and see if it works normally , if it does try erasing the data of the settings app and try a normal boot

Thanks, I have tried many different methods of entering safe mode. Method 2 on this page is pretty much what every site said and all I could do when the device is shut down. It never worked though. Long MIUI bootup screen (~100 sec), until the screen went black and then automatic boot to recovery.
That exact page additionally has method 3 though, which I have seen nowhere else before. While I tried it, there was a unusual vibration during the MIUI bootup screen. But the bootup screen still took much longer than when my phone used to be ok. I kept holding vol+ & vol- , as most websites advise to keep holding until system entered safe mode. Unfortunately, the screen went black and then showed a very scary message saying "The system has been destroyed - Press power button to shutdown".
Yeah, that was quite a shock.
When rebooting, the Xiaomi and MIUI bootscreens are as before though. Also recovery launches like before.

 

[ThatLatinGuy]

Thanks, I have tried many different methods of entering safe mode. Method 2 on this page is pretty much what every site said and all I could do when the device is shut down. It never worked though. Long MIUI bootup screen (~100 sec), until the screen went black and then automatic boot to recovery.
That exact page additionally has method 3 though, which I have seen nowhere else before. While I tried it, there was a unusual vibration during the MIUI bootup screen. But the bootup screen still took much longer than when my phone used to be ok. I kept holding vol+ & vol- , as most websites advise to keep holding until system entered safe mode. Unfortunately, the screen went black and then showed a very scary message saying "The system has been destroyed - Press power button to shutdown".
Yeah, that was quite a shock.
When rebooting, the Xiaomi and MIUI bootscreens are as before though. Also recovery launches like before.

Wow , that's a really strange message. I'm afraid that without a custom recovery you wont be able to edit the files to change the dpi from outside the system.

But since you can enter recovery mode I assume you could also enter fastboot mode. Get the fastboot drivers and install this tool

[OFFICIAL][TOOL][WINDOWS] ADB, Fastboot and Drivers - 15 seconds ADB Installer v1.4.3

15 seconds ADB Installer v1.4.3 ADB, Fastboot and Drivers What is this? This is All-in-One installer for 3 most needed PC tools for Android. No need to download big SDK for 3 small things. I originaly made it for my Kurdish friend AnGrY DuDe in...

forum.xda-developers.com

After that put your phone is on fastboot mode

If the computer detects it try the commands , you can use this tool or you could try ti change the manually

[TOOL] [NO ROOT] Change phone resolution and DPI without root.

NEW UPDATE (14-APRIL-2020) What's New? Several under the hood changes for better performance and stability. Change phone resolution and DPI without root. Devices today come with high resolution and DPI settings. Sometimes a user may want...

forum.xda-developers.com

I hope this helps , your best bet without having to factory reset is trying either adb or fastboot