another desire 626q problem. help need from XTC TEAM

HELLO XTC2 TEAM

i have another question.

My question is
ONE costomer is come to my shop. He have htc desire 626q phone. The phone is totally dead. But connect in fast boot mode. Phone chipset is MTK.

i find flash file for this phone and no any place for find flash file

And the costomer said he is going to update the phone OTA. update is stop some in 56%. After the phone is show only htc logo and restart automatically.

After that he is connect to phone in fast boot mode format device using sp flash tool. He is format bootloader section also with sp flash tool. After that phone is totally dead.

After i have received the phone i try to repairnit and i cannot do that.

But after i retuned the phone. The man is send to phone another sho.

they are repair that phone. And work totally ok

1 .My problem is how they are repair the phone? (NO ANY PLACE TO FIND FIRMARE)

2 how to write bootloader section? (IF WE WRITE FIRMWARE PHONE IS AUTOMATICALLY WRITTEN "BOOT LOADER" OR NOT?

3.Hoever if damage phone bootloader section how to write thet again?