What Is BOOT Files :

Its Allows The Host PC To Send Commands To Write Into The ONBOARD storage (eMMC, UFS).

QUALCOMM Firehose :

Is The programmer implements the Firehose protocol which allows the host PC to send commands to write into the onboard storage (eMMC, UFS). 

MTK DA File :

is Custom Download Agent that have ability to bypass Secure boot on Mediatek Devices, which allows the host PC to send commands to write into the onboard storage (eMMC, UFS).