TP450 Write SEC File

So here is a bit of history:
Phone was unlocked with octoplus box, after unlock tech guy release that imei is bad in his country.
So he try to repair, and all went ok until phone power on. Coz after imei change the phone went back to blocked state.

So now he write qcn backup back, all ok until there, after he try to write sec backup file, and this is the log:
Welcome to Octoplus/Octopus Box LG Software version 2.8.0
--------------------------------------------------------------------------------
Checking data...OK
Platform: LG Qualcomm
Selected port: COM1
Selected model: TP450
Reading info...
Could not detect mode!
Performed by 2.8.0 Software version.
--------------------------------------------------------------------------------
Checking data...OK
Platform: LG Qualcomm
Selected port: COM140
Selected model: TP450
Reading info...
Model ID: LG-TP450
IMEI: 357016-08-249694-9
Android version: 7.0
Battery level: 40%
SW Version: TP45010f
Mode: Normal
Firmware compiled date: Jul 27 2017
Firmware compiled time: 05:00:00
Firmware released date: Feb 5 2018
Firmware released time: 10:01:22
SW Version: MPSS.TA.2.3.c4-00026-8940_GEN_PACK-1
IMEI: 357016-08-249694-9
SPC: 000000
Opening "TP450_357016082496949_02-04-2018_23-15-57.SEC"...
Switching to Download mode...OK
Initializing flash...OK
Reading partitions...OK
Reading security area...OK
Backup saved to "TP450_357016082496949_02-04-2018_23-50-07.SEC"
Writing security area...
LAF Error: 80000121.
Trying second method...Failed!
LAF Error: 00000000.
Write Security Backup operation is currently not supported for your
phone's firmware.
Performed by 2.8.0 Software version.

He is downloading TP45010d version from november, can he downgrade from 2018FW to 2017 FW???

Will write SEC BACKUP FILE leave the phone in unlock state as before imei repair procedure??
and how to repair imei and stay unlocked??