Is it necessary to unlock bootloader for downgrade back to lollipop?

hello guyz i am having moto g3
recently i upgraded it to marshmallow but now i want it revert back to lollipop. My device is locked plus unrooted.
I followed all steps as mentioned here http://ift.tt/1ay1Eld
Here's what happen in command prompt-



C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash recovery recovery.img
target reported max download size of 268435456 bytes
sending 'recovery' (16484 KB)...
OKAY [ 0.718s]
writing 'recovery'...
OKAY [ 0.952s]
finished. total time: 1.669s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash partition gpt.bin
target reported max download size of 268435456 bytes
sending 'partition' (32 KB)...
OKAY [ 0.016s]
writing 'partition'...
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 0.452s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash bootloader bootloader.img
target reported max download size of 268435456 bytes
sending 'bootloader' (2546 KB)...
OKAY [ 0.109s]
writing 'bootloader'...
(bootloader) flashing sbl1 ...
(bootloader) flashing aboot ...
(bootloader) flashing tz ...
(bootloader) flashing hyp ...
(bootloader) flashing rpm ...
OKAY [ 1.638s]
finished. total time: 1.747s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash logo logo.bin
target reported max download size of 268435456 bytes
sending 'logo' (917 KB)...
OKAY [ 0.047s]
writing 'logo'...
OKAY [ 0.078s]
finished. total time: 0.125s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash boot boot.img
target reported max download size of 268435456 bytes
sending 'boot' (16384 KB)...
OKAY [ 0.686s]
writing 'boot'...
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 1.232s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash recovery recovery.img
target reported max download size of 268435456 bytes
sending 'recovery' (16484 KB)...
OKAY [ 0.706s]
writing 'recovery'...
OKAY [ 0.936s]
finished. total time: 1.642s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
0
target reported max download size of 268435456 bytes
sending 'system' (232264 KB)...
OKAY [ 9.189s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 9.663s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
1
target reported max download size of 268435456 bytes
sending 'system' (261326 KB)...
OKAY [ 10.362s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 10.418s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
2
target reported max download size of 268435456 bytes
sending 'system' (241145 KB)...
OKAY [ 9.770s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 9.817s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
3
target reported max download size of 268435456 bytes
sending 'system' (255386 KB)...
OKAY [ 10.534s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 10.631s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
4
target reported max download size of 268435456 bytes
sending 'system' (257385 KB)...
OKAY [ 10.557s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 10.607s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash system system.img_sparsechunk
5
target reported max download size of 268435456 bytes
sending 'system' (240406 KB)...
OKAY [ 9.599s]
writing 'system'...
(bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 9.653s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash modem NON-HLOS.bin
target reported max download size of 268435456 bytes
sending 'modem' (36944 KB)...
OKAY [ 1.493s]
writing 'modem'...
OKAY [ 1.010s]
finished. total time: 2.507s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot erase modemst1
erasing 'modemst1'...
OKAY [ 0.022s]
finished. total time: 0.025s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot erase modemst2
erasing 'modemst2'...
OKAY [ 0.019s]
finished. total time: 0.022s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot flash fsg fsg.mbn
target reported max download size of 268435456 bytes
sending 'fsg' (2035 KB)...
OKAY [ 0.097s]
writing 'fsg'...
OKAY [ 0.082s]
finished. total time: 0.187s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot erase cache
erasing 'cache'...
OKAY [ 0.081s]
finished. total time: 0.085s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot erase userdata
erasing 'userdata'...
OKAY [ 5.685s]
finished. total time: 5.688s

C:\Users\Personal\Downloads\Compressed\XT1550_OSPR EY_RETASIA_DS_2GB_5.1.1_LPI23
72-65_cid7_subsidy-DEFAULT_CFC.xml>fastboot reboot
rebooting...

finished. total time: 0.007s


RESULT - Phone restart with all new marshmallow.
Plese tell me what i have to do now ?
Thankyou

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