General of Redmi we always flash firmware by Fastboot mode. But sometime phone goes off can not load into Fastboot mode so we need to flash it in Download mode.
Here is my video
File size: 2.49GB
Download firmware: Xiaomi_Redmi_9_Prime_MT6768_V12.0.2.0.QJCINXM_20210319.0000.00_India_10_(by_xiaomistockrom.com).zip