adb to download mode  (Samsung)
adb reboot download

Getting information about phone
fastboot getvar all

fastboot getvar product
fastboot -i 0x17ef oem device-info (lenovo)

adb command to fastboot
adb reboot bootloader

adb command to recovery
adb reboot recovery

unlock bootloader
fastboot oem unlock-go
fastboot -i 0x17ef oem unlock-go (lenovo)

check Bootloader Status
fastboot oem device-info

fastboot flash system system.img

Flash Recovery
fastboot flash recovery images.img

Boot from images
fastboot boot twrp.img

Shutdown from ADB
adb shell reboot -p