Is Bootloader unlock is required to install software using Odin

[Rahul1250]

For downgrade  the software using Odin bootloader  unlock  is required  in samsung  smartphone 

[SliceSupport]

only when you want to downgrade to a version which is lower than the shipped one

means if your phone comes with android 9 and You want to flash with android 8.0 or android 8.1 than only bootloader needs to be unlocked

otherwise if you are installing the same or updated version no need to unlock it

bootloader unlocked allowed the app to resize the partition as per the firmware configuration

upgrading dont nees any such option to be enabled . downgrading requires it if device needs a non shipped / non deafult OS version

[Rahul1250]

I want to downgrade from one ui 2.1 to one ui 2.0 in my a51. so need to unlock bootloader or not

[A34_5G]

which device do u have?

[Rahul1250]

a51

[A34_5G]

u should try a custom rom. i have a50 and using infinity os

[Anikroyale]

Knox will be tripped, you will not have defense grade security.

[A34_5G]

@Anikroyale i think u have not watched the movie 'The return of Abhimanyu'. first watch that movie then talk about security....
things shown in the movie actually happen in real life....

[SliceSupport]

dont use custom rom . as it will wash out camera and VoLTE feature completely in samsung

in your case you dont need to unlock the bootloader .

just check the firmware region code of oneUI 2.0 as IN ( one is INDIA BRANDED and one is INDIA UNBRANDED , do some google search about CSC code meanings , Use non unbranded csc )download it and flash it using ODIN

[A34_5G]

i have volte enabled
camera quality increased
in stock rom, i had to charge my phone 2 times a day. now i charge my phone just 1 time in 2 days....
what else do u need more....
my device is now not heating.....
in stock rom, it used to heat like hell....