[General Questions and Answers] RudyGireyev:
Hello! Just received my first tablet, so am very new to all of this. :) Looking for guidance and direction. Glanced through the first page of Noob friendly thread and didn't see this addressed. So asking here.

Background: I ordered a Teclast M40 on Aliexpress and received it last week. I tried using Zoom on it and the person I was speaking to said that he could barely hear me. I then tried recording myself on the stock recording app app, and playing the file back indeed my voice was barely audible and somewhat muffled. I contacted the seller, and he sent me a Zip file asking me to reburn the stock ROM onto the Tablet thinking that this would solve the issue. I struggled with the software last week and refused to work. But this week, for whatever reason, everything worked and I was able to reflash the software. Obviously the issue was not resolved. Understanding that I am unlikely to get my money back, I now need to find a way to fix this myself, which is why I'm here.

My Questions

1. Since I have this software, do I still need to unlock the bootloader to flash a custom ROM?

2. Found a very helpful thread on Teclast M40 Here in it people talk about replacing the stock system with a gsi system. Which I never knew was an option until I came here. Since this appears less of an understaking, I'm hoping to try this first and see if it solves my microphone issue. The question is do I still need to unlock my device to install the GSI? Or can I just copy the GSI over the vbmeta.* files and burn it that way.

Just in case it is of any use here are some listings of directory entries from the Zip that I received from the Vendor I bought the Tablet from

Directory of Z:\Zoot\Teclast

01/17/2021 10:49 PM <DIR> .
01/17/2021 10:49 PM <DIR> ..
01/13/2021 12:10 AM <DIR> Firmware
01/17/2021 10:49 PM 0 rootFolder.txt
01/13/2021 12:11 AM <DIR> Upgrade Driver
01/14/2021 04:02 PM <DIR> Upgrade Tools
01/13/2021 12:11 AM 401,967 Upgrade tutorial.pdf

Directory of Z:\Zoot\Teclast\Firmware

01/13/2021 12:10 AM <DIR> .
01/13/2021 12:10 AM <DIR> ..
01/13/2021 12:11 AM 3,342,253,832 Firmware.pac

Directory of Z:\Zoot\Teclast\Upgrade Tools

01/17/2021 10:52 PM <DIR> .
01/17/2021 10:52 PM <DIR> ..
01/13/2021 12:11 AM 361 BinPack.ini
01/13/2021 12:11 AM 11,567 BMAConfig.xml
01/13/2021 12:11 AM 314,368 BMAFrame9.dll
01/13/2021 12:11 AM 1,214 BMError.ini
01/14/2021 10:09 PM 6,263 BMFileType.ini
01/13/2021 12:11 AM 290,816 BMPlatform9.dll
01/13/2021 12:11 AM 1,149 BMTimeout.ini
01/13/2021 12:11 AM 1,357 Channel.ini
01/13/2021 12:11 AM 252,928 Channel9.dll
01/13/2021 12:11 AM 266,240 CmdDloader.exe
01/13/2021 12:11 AM 228 CmdDloader.ini
01/13/2021 12:11 AM 803,727 Guide.chm
01/17/2021 09:54 AM <DIR> ImageFiles
01/13/2021 12:11 AM 2,413 MCPType.ini
01/13/2021 12:11 AM 139,264 PortHound.dll
01/13/2021 12:11 AM 196,608 ProcessFlow.dll
01/13/2021 12:11 AM 478 ProcessFlowSetting.ini
01/13/2021 12:11 AM 251,392 SecBinPack9.dll
01/13/2021 12:11 AM 244 SprdMes.ini
01/13/2021 12:11 AM 1,884,672 SprdMesApp.dll
01/13/2021 12:11 AM 120,056 udl_bkmark.bmp
01/13/2021 12:11 AM 1,763,328 UpgradeDownload.exe
01/17/2021 09:43 AM 14,385 UpgradeDownload.ini
01/17/2021 10:52 PM 0 utFolder.txt

Running the UpgradeDownload.exe extract the image files from the Firmware directory and produces the following directory

Directory of Z:\Zoot\Teclast\Upgrade Tools\ImageFiles\_DownloadFiles276766062

01/17/2021 10:54 PM <DIR> .
01/17/2021 10:54 PM <DIR> ..
01/17/2021 10:54 PM 36,700,160 boot.img
01/17/2021 10:54 PM 94,332 cache.img
01/17/2021 10:54 PM 8,388,608 dtbo.img
01/17/2021 10:54 PM 947,120 EXEC_KERNEL_IMAGE.bin
01/17/2021 10:53 PM 59,956 fdl1-sign.bin
01/17/2021 10:53 PM 632,612 fdl2-sign.bin
01/17/2021 10:54 PM 593,059 gnssmodem.bin
01/17/2021 10:54 PM 479,368 odmko.img
01/17/2021 10:54 PM 2,305,080 P20HD_EEA.bmp
01/17/2021 10:54 PM 2,305,080 P20HD_EEA.bmp(1)
01/17/2021 10:54 PM 2,097,152 persist.img
01/17/2021 10:54 PM 45,132 prodnv.img
01/17/2021 10:54 PM 41,943,040 recovery.img
01/17/2021 10:54 PM 26,214,400 SC9600_sharkl5pro_pubcp_customer_modem.dat
01/17/2021 10:54 PM 1,048,576 sharkl5pro_cm4.bin
01/17/2021 10:54 PM 6,291,456 sharkl5pro_pubcp_customer_AGCP_DSP.bin
01/17/2021 10:54 PM 1,048,576 sharkl5pro_pubcp_customer_CDMA_DSP.bin
01/17/2021 10:54 PM 2,264 sharkl5pro_pubcp_customer_deltanv.bin
01/17/2021 10:54 PM 10,485,760 sharkl5pro_pubcp_customer_DM_DSP.bin
01/17/2021 10:54 PM 20,971,520 sharkl5pro_pubcp_customer_LTEA_DSP.bin
01/17/2021 10:54 PM 765,396 sharkl5pro_pubcp_customer_nvitem.bin
01/17/2021 10:54 PM 53,796 sml-sign.bin
01/17/2021 10:54 PM 50,385,032 socko.img
01/17/2021 10:54 PM 3,124,144,944 super.img
01/17/2021 10:54 PM 1,940 teecfg-sign.bin
01/17/2021 10:54 PM 2,213,892 tos-sign.bin
01/17/2021 10:54 PM 632,612 u-boot-sign.bin
01/17/2021 10:54 PM 63,140 u-boot-spl-16k-sign.bin
01/17/2021 10:54 PM 32,545 ums512_1h10.xml
01/17/2021 10:54 PM 147,772 userdata.img
01/17/2021 10:54 PM 1,048,576 vbmeta-sign.img
01/17/2021 10:54 PM 4,096 vbmeta_system.img
01/17/2021 10:54 PM 4,096 vbmeta_vendor.img