So, as we know with recent MIUI update Xiaomi screwed our whyred. And this gave birth to many questions which is like a struggle for many users to find all those answers. So, I tried to answer all your questions. If you think your question isn't included please feel free to ask.
Q1: What is this "Anti-Rollback" thing?
A: Its a security measure that Google brought with the release of Android Oreo. It makes sure that your data is secure even when phone is stolen or if any attacker tries to downgrade the software and wants to gain control over your data.
Q2: How is this harmful to my device?
A: Well, as a security measure it should never give you a hard-brick. When someone tries to downgrade, it should display a warning and get turned off but there's difference between how things should work and how Xiaomi does. As Google has stated, "Anti-Rollback" should get automatically turn off when the user unlocks the bootloader but in case of MIUI even unlocked users are getting hard-bricks. Hopefully the developers of MIUI should push an update soon and if they don't, our beloved devs will find a way for sure
Q4: So, what now? Will Xiaomi solve this issue?
A: We do not know. But our beloved developers in the XDA-Forum will find a way for sure
Q5: How to know if my device is affected by it?
A: Run fastboot command :
fastboot getvar anti
Q6: I'm in the Anti-Rollback squad what now?
A: Don't worry you can still flash custom recovery and roam around custom ROMs but avoid flashing any firmware or any MIUI ROM which is older than what you're using now otherwise you'll brick your device.
Q7: Which MIUI builds include "Anti-Rollback"?
A: All the MIUI builds which are released after Stable MIUI V220.127.116.11 and Beta MIUI V8.7.5 include "Anti-Rollback". And yes the Chinese versions are affected as well.
Q8: Do MIUI Stable V18.104.22.168 and Beta V8.7.5 have "Anti-Rollback" enabled?
A: NO. If you're on either of these builds you are safe to downgrade and use any older version.
Q9: How to flash custom recovery and custom ROMs on "Anti-Rollback" enabled devices?
A: On "Anti-Rollback" enabled ROMs you cann't flash custom recovery permanently. You'll have to boot into recovery first by running fastboot command:
fastboot boot xyz.img
Q10: Can I migrate from Stable to Beta and vice-versa?
A: You can install Beta from Stable, make sure you flash latest Beta build same is the case with Stable. If you're on anti-4 firmware, whether its Beta or Stable you can switch to any anti-4 MIUI ROM Beta or Stable but remember you must flash latest version available while switching. (anti-4 means "Anti-Rollback" enabled firmware)
Q11: Can I unlock bootloader and flash custom ROMs on an "Anti-Rollback" enabled device?
A: Yes. Again to flash custom ROMs and recovery refer to Q9.
Q12Can I flash "Anti-Rollback" enabled ROM via TWRP?
AWell, in some cases it did work, just flash lazy flasher zip file after flashing MIUI ROM via TWRP. But while switching to MIUI from AOSP based ROMs on an "Anti-Rollback " enabled device I recommend you to go with fastboot method to avoid chances of brick.
For active discussion join whyred telegram group: https://t.me/redminote5proofficial
Hit thanks if helped.