In the same way as you flashed the rom but by checking the "clean all and lock" box which is activated by default on Miflash or"flash_all_lock.bat"directly without Miflash.
Yep,normally, I saw that for certain devices, it was the Google dialer, not having this device I cannot confirm it 100%. On the other hand, for the Xiaomi EU rom it is 100%.
Nope, to change region, use a Fastboot ROM with Miflash (will erase all data) and above all have the bootloader unlocked (will erase all data).
Package Name: gauguin_tw_global_images_V14.0.1.0.SJSTWXM_20230426.0000.00_12.0_global_99359cebf9.tgz
The title is "Install Mi Dialer Call Record Xiaomi Poco Without Unlock Bootloader No Data Loss [English]"
Look at 7 minutes 52 the padlock is open so the bootloader is unlocked.
I don't know what you're talking about, the title of the link is for the Xiaomi 13 but the link leads to a post concerning the Xiaomi 14 which has been unlocked.